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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>A socio-technical perspective on forensic challenges in smartphones and smartwatches: A systematic literature review⋆</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Jonas Ingemarsson</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Erik Andersson</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Joakim Kävrestad</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Marcus Birath</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Jönköping School of Engineering, Jönköping University</institution>
          ,
          <addr-line>Gjuterigatan 5, 553 18 Jönköping</addr-line>
          ,
          <country country="SE">Sweden</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>University of Skövde</institution>
          ,
          <addr-line>Högskolevägen 1, 541 28 Skövde</addr-line>
          ,
          <country country="SE">Sweden</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2025</year>
      </pub-date>
      <abstract>
        <p>With the increasing use of smartphones and smartwatches, these devices have become vital sources of digital evidence in forensic investigations, as they often act as “silent witnesses” to events. Thus, it is important to understand the unique challenges they pose-individually and in combination. This paper reports on a systematic literature review to examine how these devices relate to current forensic challenges, identify potential diferences between the devices and future research needs. From 73 relevant articles, thematic analysis identified four main themes and related sub-themes for each device. The review considers not only technical constraints, but also the broader context in which these devices are used and investigated, ofering a socio-technical lens on digital forensics. The findings shows that challenges related to smartphones are more frequently discussed than those to smartwatches. This may be due either to smartphones' greater complexity or to limited research on smartwatchesthe latter being more likely based on the volume of published work. This review provides a structured overview of the forensic landscape and identifies key gaps for future study.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Digital forensics</kwd>
        <kwd>smartphones</kwd>
        <kwd>smartwatches</kwd>
        <kwd>forensic challenges</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        In digital forensics, smartphones and smartwatches have become valuable sources of evidence in
crime and incident investigations. In addition to be carriers of traditional forensic artifacts such as
communication data and pictures, they are often so called “slient witnesses” of crimes. For instance, in
the Caroline Crouch case, data from her smartwatch showed heartbeats after her husband claimed she
was dead, while his phone showed movement despite claiming to be tied up [
        <xref ref-type="bibr" rid="ref1 ref2">1, 2</xref>
        ]. This type of data,
called gait or sensor data, is collected by the devices without actions needed on the part of the user.
Such data can, as in the Caroline Crouch case, provide key evidence in criminal investigation. How gait
data is stored can difer between devices and application. It is, for instance, common that a smartwatch
maintains some limited internal memory while continuously synchronizing with a smartphone or cloud
service. Consequently, we consider both smartwathches and smartphones in this research.
      </p>
      <p>
        Reliable figures on smartwatch adoption remain unclear. Laricchia [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ] forecasted 225 million users
in 2024, while others estimate nearly double that [
        <xref ref-type="bibr" rid="ref4 ref5">4, 5</xref>
        ]. Smartwatches collect health-related and
notification data [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ], and with over 5.31–5.75 billion smartphone users worldwide [
        <xref ref-type="bibr" rid="ref7 ref8">7, 8</xref>
        ], both device
types are crucial in forensic investigations as these devices can store key digital evidence [
        <xref ref-type="bibr" rid="ref10 ref7 ref9">9, 10, 7</xref>
        ].
      </p>
      <p>Given their widespread use, it is important to understand the challenges of investigating these
devices, but also the diference between them. This study investigates these diferences by conducting a
systematic literature review, identifying current challenges, gaps, and future research opportunities.</p>
      <p>While smartphones are well-studied, smartwatch forensics is emerging. A systematic literature review
is appropriate for synthesizing available research.</p>
      <p>
        This study follows the three-phase model by Kitchenham and Charters [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ], incorporating the six
steps by Paré and Kitsiou [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ], and uses thematic analysis [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ] to identify challenge patterns. The
analysis adopts a socio-technical lens where we perceive digital forensics as a socio-technical process.
While the technical capability to extract and analyze digital information is central, forensic capabilities
are impacted by social aspects including regulations as well as formal and informal organizational
structures.
      </p>
      <p>The remainder of this paper is structured as follows: Section 2 provides background on the topic,
introducing key concepts and establishing a solid foundation for understanding the results and
conclusions. Section 3 outlines the methodology used in this study, which is a structured literature review. It
details the process of data collection and analysis. Section 4 presents the findings, including the results
of the thematic coding and the main research insights. In Section 5, the results are discussed, including
the researchers’ reflections and elaborating on the socio-technical dimensions of the study—highlighting
a paradox. Section 6 answers the research question by presenting the conclusions and limitations of the
study. Finally, Section 7 outlines directions for future research.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Background</title>
      <sec id="sec-2-1">
        <title>2.1. Smartphones</title>
        <p>
          Due to their widespread use and multifunctionality, smartphones are valuable sources of digital evidence
in forensic investigations. Despite diferences in brand, OS, and hardware, they typically contain similar
categories of data: internal storage, SIM information, messages, location, social media activity, call logs,
multimedia, and network data [
          <xref ref-type="bibr" rid="ref14">14</xref>
          ].
        </p>
        <p>
          Smartphones also collect gait data—patterns of human movement such as walking or climbing stairs.
This data, captured through sensors like accelerometers and gyroscopes, is known as on-body gait and
is stored by Inertial Measurement Units (IMUs) embedded in smartphones and smartwatches [
          <xref ref-type="bibr" rid="ref15">15</xref>
          ]. These
always-on sensors can without drawing attention capture continuous motion data [
          <xref ref-type="bibr" rid="ref16">16</xref>
          ]. Because gait
cycles are unique to individuals, this data can be used for biometric identification [
          <xref ref-type="bibr" rid="ref17 ref18">17, 18</xref>
          ]. Gait-based
biometrics are already applied in forensic contexts for identification and verification. For instance,
Ghosh et al. [
          <xref ref-type="bibr" rid="ref19">19</xref>
          ] found that gait patterns while walking and typing, as recorded by smartphones, could
help identify individuals and infer demographic traits like age and gender.
        </p>
      </sec>
      <sec id="sec-2-2">
        <title>2.2. Smartwatches</title>
        <p>Smartwatches are wearable devices that extend smartphone functionalities and ofer real-time access
to data, apps, and notifications [ 20, 21]. Unlike traditional watches, they can run mobile applications,
provide fitness tracking, and support messaging and calls. Their popularity has grown significantly
over the past decade [20].</p>
        <p>
          Smartwatches collect substantial personal data through sensors, including heart rate, steps, and
location. This data can be useful in forensic investigations [
          <xref ref-type="bibr" rid="ref6">22, 6</xref>
          ]. Stored information may include
messages, contacts, call logs, notifications, and health metrics [
          <xref ref-type="bibr" rid="ref6">6, 23, 24</xref>
          ]. Location data from GPS and
movement records can also help verify or disprove alibis [25, 26].
        </p>
        <p>Like smartphones, smartwatches contain sensors such as accelerometers and gyroscopes, which
can capture gait data for biometric identification [ 27, 28, 29]. Their consistent position on the body
improves gait measurement accuracy. Other sensors-like heart rate monitors, GPS, microphones, and
ambient light sensors—add further forensic value [30]. For example, smartwatch data was used in a
rape case where the movement recorded contradicted the reported timeline, resulting in charges against
the complainant [26, 31].</p>
        <p>Because smartwatches operate passively in the background, they continuously collect potentially
incriminating or exonerating evidence, such as physical activity or physiological data. These digital
traces are increasingly relevant in cases involving suspicious deaths, aviation incidents, and legal
disputes [30, 32].</p>
      </sec>
      <sec id="sec-2-3">
        <title>2.3. Gait data</title>
        <p>Both smartphones and smartwatches are equipped with sensors such as accelerometers, which collect
gait—or sensory—data. This data can support or refute alibis and contribute to hypothesis development
in digital investigations [33]. These sensors provide both direct evidence, like GPS location, and indirect
evidence, such as determining whether someone is indoors based on light sensor data.</p>
        <p>
          Modern personal devices store large volumes of sensory information, particularly IMU data, which
can be used for biometric identification through gait analysis. Gait refers to movement patterns such
as walking or climbing stairs and can be classified into two types: visual gait, captured via external
cameras, and on-body gait, collected by sensors embedded in devices worn on the body [
          <xref ref-type="bibr" rid="ref15">15</xref>
          ].
        </p>
        <p>
          As users carry or wear these devices daily, they continuously log data useful for activity recognition,
health monitoring, and authentication [
          <xref ref-type="bibr" rid="ref15">15</xref>
          ]. Gait analysis has proven valuable in criminal investigations,
as demonstrated in a case where gait patterns helped identify and convict a bank robber [34].
        </p>
      </sec>
      <sec id="sec-2-4">
        <title>2.4. Digital evidence</title>
        <p>Digital evidence is relevant in nearly all types of crimes—whether cyber-related or traditional—since
modern life constantly generates digital traces [35, 36, 37]. Even crimes committed ofline may leave
behind digital records, such as CCTV footage, GPS logs, transit receipts, or photos taken by bystanders
[36].</p>
        <p>Devices like smartphones often contain digital evidence, including location data, messages, call logs,
and photos. They also gather sensory data such as activity recognition and gait patterns [35]. Similarly,
smartwatches can hold information like heart rate, step count, messages, emails, and other personal
data [38].</p>
        <p>Harbawi and Varol [25] defines digital evidence as any data transferred through an electronic system.
This may include documents, videos, browsing histories, social media activity, financial records,
esignatures, or even online appointments.</p>
      </sec>
      <sec id="sec-2-5">
        <title>2.5. Digital forensics</title>
        <p>Digital forensics involves identifying “what has happened” by analyzing digital devices for evidence
of criminal activity [36]. Flaglien et al. [39] describes it as a science-based process to preserve, collect,
examine, and present digital evidence to reconstruct events or predict unauthorized actions.</p>
        <p>As society becomes more digitized, digital forensics plays a role in most legal cases, involving data
from smartphones, emails, GPS logs, or credit card transactions. Due to the volatility of some evidence
types, standardized tools and procedures are essential [39].</p>
        <p>
          In smartphone forensics, standard techniques apply, but should also include data specific to mobile
devices, such as gait and sensor data [35]. For smartwatches, however, no universal forensic standard
exists [40, 36]. Researchers propose custom frameworks for these devices [
          <xref ref-type="bibr" rid="ref6">22, 6, 40</xref>
          ], often placing
them within IoT forensics [24, 41], which is defined as: “an especial branch of digital forensics, where
the identification, collection, organization, and presentation processes deal with the IoT infrastructures to
establish the facts about a criminal incident” [42, p.280].
        </p>
        <sec id="sec-2-5-1">
          <title>2.5.1. The digital forensics process</title>
          <p>Digital forensics involves collecting, analyzing, and reporting on digital data [36]. The process is
generally divided into three phases, each described below.</p>
          <p>Collect (Phase 1): This phase involves obtaining digital evidence from a target person, device,
or location. Typically executed under a search warrant, investigators search for digital devices like
smartphones, smartwatches, or hard drives that may hold relevant data [36].</p>
          <p>Analyze (Phase 2): Here, forensic experts examine the collected data to reconstruct events or
understand digital activity. This analysis is guided by specific questions from investigators, which help
define the scope and legal boundaries of the examination [36].</p>
          <p>Report (Phase 3): The final phase presents the findings in response to the investigator’s questions.
It is important to clearly distinguish facts from conclusions. This phase may prompt new questions,
making the analysis and reporting stages iterative [36].</p>
        </sec>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>3. Methodology</title>
      <p>
        Based on the purpose of this study, a structured literature review was conducted following the three
phases proposed by Kitchenham and Charters [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ] and the six-step approach outlined by Paré and
Kitsiou [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ]. To identify relevant literature, two search queries were constructed. The queries used
were (smartwatches OR "smart watches") and (smartphones OR "smart phones"), both followed by AND
("digital forensics" OR forensics OR forensic). The intention was to capture as much relevant literature as
possible, regardless of the specific combination used. References to challenges, obstacles, and similar
concepts were intentionally omitted from the search strings in order to also retrieve articles where such
challenges were identified as byproducts of research in the field.
      </p>
      <p>The search strings were applied in five databases on 23 March 2025: ACM Digital Library, Emerald
insight, IEEE Xplore, Scopus, and Web of Science. The search was restricted to include only conference
papers and journal articles published from 2020 onward. Papers failing to meet the following inclusion
criteria were excluded: peer-reviewed, written in English, and relevant to the topic, i.e., identifying
current challenges. Articles with a primary focus other than smartwatches and/or smartphones were
removed (e.g., those focusing on forensic identification or authentication of specific media types such
as PRNU-based image source identification). Previous review articles were included in this study—but
only if data could be extracted from their primary data.</p>
      <p>
        Further, the screening process was carefully documented using a PRISMA flowchart (Figure 1), based
on procedures established by Page et al. [43] and generated using a tool developed by Haddaway et al.
[44]. The papers included in the study were analysed using thematic coding [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ], as follows1:
1. Each paper was read in its entirety, and relevant sections were marked with labels (codes) that
emerged inductively from the data.
2. Codes that related to one another were grouped into broader sub-themes, which also emerged
inductively from the data.
3. Sub-themes that shared conceptual similarities were then merged into overarching themes, which
likewise emerged inductively from the data.
      </p>
      <p>The articles cited in the results are those that passed this review and coding process.</p>
    </sec>
    <sec id="sec-4">
      <title>4. Results</title>
      <p>This section presents the four identified themes from the thematic analysis for both smartphones
and smartwatches, along with their associated sub-themes and codes. In total, eight sub-themes were
identified for smartphones and seven for smartwatches. For both technologies, the theme legal challenges
includes only a single code and therefore no sub-theme was formed. Each subsection below provides a
detailed discussion of the themes, their sub-themes, and the corresponding codes for each device. An
overview of themes, sub-themes, and codes can be seen in Table 1.</p>
      <sec id="sec-4-1">
        <title>4.1. Technical challenges</title>
        <p>This theme includes four sub-themes: digital forensics workflow, forensic tool challenges, technological
evolution, and evidence acquisition.
1A sample of the coding can be found in Table 2</p>
        <p>Identification of new studies via databases and registers
n
o
it
a
c
iitf
n
e
d
I</p>
        <p>Records identified from:</p>
        <p>Databases (n = 5):</p>
        <p>IEEE Xplore (n = 350)
ACM Digital Library (n = 268)</p>
        <p>Emerald (n = 139)</p>
        <p>Scopus (n = 437)
Web of Science (n = 229)</p>
        <p>Records screened</p>
        <p>(n = 1,051)
Reports sought for retrieval</p>
        <p>(n = 189)
Reports assessed for eligibility</p>
        <p>(n = 165)
New studies included in review
(n = 73)</p>
        <p>Records removed before screening:</p>
        <p>Duplicate records (n = 372)</p>
        <p>Records excluded</p>
        <p>(n = 862)
Reports not retrieved</p>
        <p>(n = 24)
Reports excluded:
Criteria 1 (n = 1)
Criteria 4 (n = 67)
Criteria 5 (n = 24)</p>
        <sec id="sec-4-1-1">
          <title>4.1.1. Smartphones</title>
          <p>The first sub-theme, digital forensics workflow, concerns challenges related to the forensic process
itself—whether due to the vast volume of data or the fact that devices under investigation may still be
active and continue to generate data. Eight codes were identified. Rooting/jailbreaking refers to obtaining
elevated permissions on a device to enable physical acquisition, which can enhance evidence recovery.
However, this process introduces risks, such as compromising the device’s integrity or causing data loss
[45, 46]. When rooting or jailbreaking is not possible, important artefacts may remain unrecovered, and
physical acquisition becomes infeasible [47, 48]. Another issue is cloud data, which presents acquisition
dificulties due to its distributed nature and the sheer volume of data typical of cloud-linked smartphone
storage [49, 50].</p>
          <p>
            The size of data itself presents analytical challenges, as investigators must manage and interpret large,
diverse datasets [
            <xref ref-type="bibr" rid="ref10">10, 51, 48, 52</xref>
            ]. Relatedly, dificulties arise from foreign apps and languages, which can
introduce delays and risks of misinterpretation [53, 52]. Physical acquisition methods are also challenged
by their cost, complexity, and time demands [45].
          </p>
          <p>Moreover, traditional post-mortem analysis approaches are often unsuitable due to the real-time
and interactive nature of smartphones [54]. Finally, data interpretation remains a core dificulty, as
Rooting/jailbreaking*, Cloud data*, Size of
data*, foreign apps and languages*,
physical acquisition*, post-mortem analysis
limitations*, data interpretation*, syncing
device with the cloud**, live devices**
Tool limitations, tool reliability*, lack of
tools*, special tools*, incomplete data
recovery*
device infrastructure fragmentation, ever
evolving technology,
Troubles accessing certain data*,
diference between rooted and unrooted*,
reliability issues for evidences*, volatile
evidence, evidence damaged*, login
activities*, user-controlled data limitations*
Encryption, anti-forensic techniques and
data wiping*
Authentication*, security features*
lack of standardisation*, linking data to
real identities*, inadequate methods*, no
standard for wearable tech**,
Vocabulary limitations*, limited sample
number*
Lack of research**, finding datasets**</p>
          <p>Legal issues
Forensic tool challenges
Technological evolution</p>
          <p>Evidence acquisition
Anti-forensics challenges</p>
          <p>Data protection and anti-forensics</p>
          <p>Security*
Methodological and devel- Method
opment challenges
Legal challenges</p>
          <p>Development constraints*
Research constraints**
n/a
investigators must navigate diverse formats and artefacts across apps and systems [55, 52].</p>
          <p>
            The second sub-theme, forensic tool challenges, focuses on limitations of the tools employed in mobile
forensics. Tool limitations are prominent, particularly when tools lack support for certain artefacts,
operating systems, or applications [
            <xref ref-type="bibr" rid="ref10 ref20">56, 45, 10, 57, 53, 58, 59, 47, 60, 61, 62, 63</xref>
            ]. High costs and system
requirements can further restrict tool accessibility [51].
          </p>
          <p>
            Tool reliability also poses a concern due to inconsistent performance in evidence recovery and
common issues such as slow updates, bugs, and inefective filtering [
            <xref ref-type="bibr" rid="ref10">10, 64, 65, 66, 51, 67, 46, 53</xref>
            ]. In
addition, investigators often face a lack of tools suited for handling large datasets or specialised scenarios
[49, 52]. Some tasks require special tools, particularly for physical extractions, which allow for more
comprehensive data retrieval [51]. Nonetheless, even with advanced tools, incomplete data recovery
may occur, resulting in loss of critical artefacts [68].
          </p>
          <p>
            The third sub-theme, technological evolution, relates to the pace of technological change and its
implications for forensic practice. Device infrastructure fragmentation poses significant challenges, as
investigators must contend with a variety of operating systems [
            <xref ref-type="bibr" rid="ref20">56, 49, 57, 55</xref>
            ], hardware platforms,
and proprietary software structures [45]. This includes dificulties linked to unique file systems [ 69],
data discrepancies across services [70], and the fragmentation of device models and manufacturers
[
            <xref ref-type="bibr" rid="ref9">71, 72, 9, 73, 74, 75</xref>
            ]. Keeping up with evolving services further adds to this burden [76].
          </p>
          <p>
            Ever evolving technology amplifies this challenge by making it dificult to ensure that forensic tools
and methods remain compatible with emerging technologies [
            <xref ref-type="bibr" rid="ref9">45, 49, 50, 72, 9, 77, 65, 78, 63, 79, 73</xref>
            ].
          </p>
          <p>The final sub-theme under technical challenges is evidence acquisition, consisting of seven codes.
Troubles accessing certain data include obstacles in retrieving specific data stored on mobile devices
[45, 75]. A related issue is the diference between rooted and unrooted devices, which afects the volume
and type of data that can be accessed [80, 81, 82, 83, 84, 85, 86, 87, 88, 89]. Unlike the earlier discussion
about rooting that focused on gaining elevated privileges through rooting, this relates to the practical
efects for data extraction—specifically, how the device’s rooted status determines the types and volume
of data that forensic tools can retrieve.</p>
          <p>The complexity of digital data also introduces reliability issues for evidences, where artefacts may be
misinterpreted or lack verifiable accuracy [ 90, 91]. Another challenge is the presence of volatile evidence,
which is vulnerable to loss or alteration if not captured promptly [49, 76, 92, 55, 93, 94, 81]. In some
instances, evidence may be damaged during acquisition, further impacting evidentiary completeness
[64].</p>
          <p>Login activities are also dificult to identify and confirm, making it challenging to attribute actions to
specific users [ 76]. Lastly, user-controlled data limitations reflect the risks associated with users deleting,
modifying, or encrypting their data before or during forensic procedures [74].</p>
        </sec>
        <sec id="sec-4-1-2">
          <title>4.1.2. Smartwatches</title>
          <p>The first sub-theme, digital forensics workflow, includes challenges associated with the dynamic nature
of smartwatches and their integration with external systems. One issue is syncing device with the cloud,
where syncing Fitbit devices with cloud services at specific times complicated the forensic analysis by
introducing inconsistencies in the data timeline [40]. Additionally, the challenge of live devices arises
when devices remain active during the investigation, potentially continuing to collect data and thereby
compromising the integrity of the evidence [40].</p>
          <p>The next sub-theme, forensic tool challenges, relates to the limitations of tools employed in smartwatch
investigations. Tool limitations were noted where commercial and traditional forensic tools failed
to access all storage locations or accurately recover and decode artefacts from smartwatches [95].
Furthermore, these tools may lack support for certain data types or process data incorrectly, reducing
the reliability and completeness of the extracted evidence [96].</p>
          <p>The third sub-theme, technological evolution, reflects how the rapid pace and diversity of consumer
electronics complicate forensic practices. Device infrastructure fragmentation makes it dificult to conduct
comprehensive research or develop tools compatible with the wide array of available smartwatch models
[73]. Adding to this, the issue of ever evolving technology highlights the ongoing need for forensic
investigators to continuously update their knowledge and adapt to newly introduced technologies [40].</p>
          <p>The fourth and final sub-theme, evidence acquisition, focuses on the limited accessibility and temporal
nature of certain types of smartwatch data. Volatile evidence was identified as a major challenge, with
some data being retained for only short periods—such as 13 to 15 days—before it becomes permanently
inaccessible, thereby narrowing the window of opportunity for successful evidence collection [96].</p>
        </sec>
      </sec>
      <sec id="sec-4-2">
        <title>4.2. Anti-forensic challenges</title>
        <p>This theme entails obstacles that hinder the collection and analysis of digital evidence. For smartphones,
this theme includes two sub-themes: data protection and anti-forensics and security, which cover
challenges such as encryption, data wiping, and various anti-forensic techniques. For smartwatches,
the theme similarly addresses these obstacles but includes only the sub-theme data protection and
anti-forensics.</p>
        <sec id="sec-4-2-1">
          <title>4.2.1. Smartphones</title>
          <p>
            The first sub-theme, data protection and anti-forensics, addresses deliberate or systemic obstacles to
forensic investigations. A key challenge is encryption, where encrypted files and data render information
unreadable or inaccessible to both investigators and forensic tools [
            <xref ref-type="bibr" rid="ref10">45, 10, 49, 54, 97, 66, 98, 48, 89, 99, 55,
79, 46, 100, 101</xref>
            ]. This challenge highlights the need for forensic tools capable of decrypting protected
content [53]. Closely related are anti-forensics techniques and data wiping, which refer to the deliberate
use of apps or tools to delete, conceal, or alter data to obstruct investigations [
            <xref ref-type="bibr" rid="ref10 ref7">45, 102, 10, 49, 7, 103, 92,
97, 72, 66, 86, 104, 88, 105, 74</xref>
            ]. These activities require efective countermeasures [ 53]. Additionally,
foreign applications may be used as anti-forensic tools, introducing further complexity [52], while some
suspects employ anti-reverse engineering techniques to prevent forensic analysis [106].
          </p>
          <p>
            The second sub-theme, security, includes device-level and software-level protective mechanisms
that hinder forensic access. The first issue, authentication, involves access barriers such as PINs and
passcodes that prevent entry into devices [45, 72, 69]. Many Android devices, in particular, feature lock
screens that remain resistant to current forensic techniques, requiring the development of improved
access methods [53, 74]. The second issue, security features, refers to embedded protections at the device
or application level that restrict access to data. These include security protocols, app-level restrictions,
and regular security updates that can interfere with evidence retrieval eforts [
            <xref ref-type="bibr" rid="ref9">49, 54, 97, 9, 99, 98, 84</xref>
            ].
          </p>
        </sec>
        <sec id="sec-4-2-2">
          <title>4.2.2. Smartwatches</title>
          <p>
            The sub-theme data protection and anti-forensics focuses on challenges that hinder forensic
investigation, often unintentionally, such as encryption, which protects user privacy but can also conceal
evidence. Within this sub-theme, the code encryption was identified, referring to dificulties in accessing
information stored in encrypted files [107] or data rendered inaccessible due to encryption [
            <xref ref-type="bibr" rid="ref6">108, 6</xref>
            ].
          </p>
        </sec>
      </sec>
      <sec id="sec-4-3">
        <title>4.3. Methodological and development challenges</title>
        <p>The theme methodological and development challenges includes two sub-themes related to the approaches
and limitations in forensic investigation. For smartphones, these sub-themes are method and development
constraints, addressing challenges such as the lack of standardisation across operating systems, file
formats, and the dificulties in developing new methods or tools. For smartwatches, the sub-themes
are method and research constraints, focusing on challenges in the methods applied specifically to
smartwatches as well as broader research and development limitations within the field.</p>
        <sec id="sec-4-3-1">
          <title>4.3.1. Smartphones</title>
          <p>
            The first sub-theme, method, includes various methodological challenges in smartphone forensics. One
major issue is the lack of standardisation, which arises from the absence of a unified forensic approach
that extends beyond the operating system level [
            <xref ref-type="bibr" rid="ref20">56</xref>
            ]. This includes the limited availability of techniques
supporting diverse platforms [
            <xref ref-type="bibr" rid="ref10">10</xref>
            ], the lack of standardised data collection procedures [
            <xref ref-type="bibr" rid="ref7">7</xref>
            ], and the
absence of consistent forensic file formats [ 53]. Another methodological concern is linking data to real
identities, which reflects the dificulty of associating digital artefacts with the actual perpetrators of a
crime. Furthermore, the use of inadequate methods presents technical obstacles, such as synchronisation
issues between metadata and flash storage during the data acquisition process [
            <xref ref-type="bibr" rid="ref20">56</xref>
            ].
          </p>
          <p>The second sub-theme, development constraints, focuses on challenges afecting the advancement of
forensic tools and techniques. Vocabulary limitations hinder the accuracy of classification tasks due to a
restricted word set, which limits the system’s ability to distinguish between relevant and irrelevant
data [109]. Similarly, a limited sample number undermines the performance of forensic algorithms,
particularly when only a small number of vault applications are available for analysis [110].</p>
        </sec>
        <sec id="sec-4-3-2">
          <title>4.3.2. Smartwatches</title>
          <p>The first sub-theme, method, identifies the absence of established procedures as a core limitation in
smartwatch forensics. Specifically, the code no standard for wearable tech reflects the lack of a recognised
framework for conducting investigations on wearable devices. This creates dificulties for investigators
in locating and analysing all relevant data, which can compromise the accuracy and integrity of findings
[40].</p>
          <p>The second sub-theme, research constraints, relates to limitations in the current state of forensic
research on smartwatches. One challenge is the lack of research, as many widely used smartwatch
models have not yet been thoroughly examined, increasing the likelihood that relevant artefacts remain
unidentified [ 81]. A related issue is finding datasets, which refers to the dificulty in accessing extended
datasets that reflect real-world usage patterns—essential for validating forensic techniques [111].</p>
        </sec>
      </sec>
      <sec id="sec-4-4">
        <title>4.4. Legal challenges</title>
        <sec id="sec-4-4-1">
          <title>4.4.1. Smartphones</title>
          <p>
            The fourth and final theme, legal challenges, relates to laws and regulations that may restrict investigators’
ability to access or utilize certain information. As only a single code, legal issues, was identified, no
sub-themes were formed under this theme for either smartphones or smartwatches.
The code legal issues highlights the legal complexities involved in smartphone forensics. Information
retrieved from smartphones is often highly sensitive and potentially admissible in court; however, its
use is governed by strict legal frameworks designed to protect user privacy [49]. Additional dificulties
arise due to the evolving nature of corporate policies that determine how, and under what conditions,
digital evidence may be shared with law enforcement agencies [
            <xref ref-type="bibr" rid="ref9">9</xref>
            ]. Furthermore, accessing specific user
information often requires formal legal procedures, such as obtaining subpoenas from Internet Service
Providers (ISPs), which can delay investigations [58].
          </p>
        </sec>
        <sec id="sec-4-4-2">
          <title>4.4.2. Smartwatches</title>
          <p>The same code legal issues, also applies to smartwatch forensics. A key issue concerns the
timeconsuming process of data retrieval from user accounts. Although it is technically possible to download
archived data, the steps involved in verifying legal requests and receiving the requested information
from service providers can take several weeks or even months, thereby delaying the timeliness of
forensic investigations [40].</p>
        </sec>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>5. Discussion</title>
      <p>The challenges identified in this study align with previous reviews on mobile forensics. Sharma
et al. [74] highlights obstacles such as lock screen authentication and remote data wiping after device
seizure, while Fukami et al. [97] underscores encryption, data wiping, and security features as major
barriers. This study confirms these persistent challenges, including the complexity posed by diverse
smartphone models [74], and adds further issues related to legal constraints and tool limitations. For
smartwatches, the lack of forensic research corresponds with observations by Rightley and Karabiyik
[81] and Al-Sharrah et al. [22]. Unlike prior work, this review uniquely integrates challenges across
both smartphones and smartwatches, revealing smartwatch-specific issues not previously reported.</p>
      <p>This study focuses on the socio-technical side, highlighting how technology and social values work
together and impact society. For example, encryption emerges as a major challenge for forensic
investigations across both smartphones and smartwatches. While encryption prevents forensic investigators from
accessing potentially crucial evidence—thus potentially enabling criminal activity to go undetected—it
simultaneously serves a critical function for everyday users seeking to protect their privacy and secure
sensitive information, as well as being a default setting on many devices and services used in a modern
digital society.</p>
      <p>This paradox reveals the socio-technical complexity of encryption challenges in digital forensics,
where eforts to overcome such challenges may both strengthen legal processes and contribute to
positive societal outcomes. Therefore, while this study aims to contribute valuable insights into current
forensic challenges, it also acknowledges the broader social trade-ofs involved, particularly concerning
individuals’ digital rights and privacy in an increasingly interconnected world.</p>
    </sec>
    <sec id="sec-6">
      <title>6. Conclusion and limitations</title>
      <p>This study aimed to identify current challenges in digital forensic analysis of smartphones and
smartwatches and answer the question: “How do the challenges in forensic analysis difer between smartphones
and smartwatches?” A systematic literature review was conducted, analysing 73 articles from five
databases through thematic coding.</p>
      <p>The results showed significantly more challenges identified for smartphones than for smartwatches.
This suggests that smartphone forensics presents a broader and more discussed set of challenges. Two
hypotheses explain this diference: ( H1) smartphones are inherently more complex, or (H2) there is
less research on smartwatches, so many challenges remain unidentified. The second, H2, is more likely
given the diference in the amount of published articles. Some challenges are device-specific—such as
ifnding datasets for smartwatches—while others like authentication appear for smartphones but were
not identified for smartwatches, possibly due to less secure lock screens or less research focus.</p>
      <p>Limitations include terminology overlap—terms like smartwatches, fitness trackers, wearables, and
IoT were sometimes used interchangeably in the literature, which may have led to missing relevant
studies. Future searches could refine terms to improve coverage.</p>
      <sec id="sec-6-1">
        <title>6.1. Smartphones</title>
        <p>Thematic coding for smartphones revealed four main themes and eight sub-themes. The most frequent
codes were anti-forensic techniques and data wiping (20) and encryption (16). Smartphones had 36
identified challenges, more than triple the 11 challenges found for smartwatches. Some challenges,
such as bypassing PIN codes, were expected to appear for smartwatches but did not, again pointing
to possible research gaps. Smartphones also had more published studies, reflecting greater research
attention.</p>
      </sec>
      <sec id="sec-6-2">
        <title>6.2. Smartwatches</title>
        <p>For smartwatches, seven sub-themes emerged, with encryption (3) and tool limitations (2) as the most
mentioned challenges. The smaller number of challenges corresponds with fewer published articles.
Device-specific challenges for smartwatches included no standard for wearable tech and lack of research,
underscoring the early stage of smartwatch forensics. Encryption was a shared challenge for both
devices. As research progresses, smartwatches will likely present new, unique challenges requiring
tailored forensic methods.</p>
      </sec>
    </sec>
    <sec id="sec-7">
      <title>7. Future research</title>
      <p>Smartwatch forensics is under-researched, as shown by the small number of identified challenges and
articles. Future studies should include additional databases to capture more comprehensive challenges,
especially for smartwatches. Clarifying terminology around smartwatches, fitness trackers, and
wearables will also aid research clarity. Since encryption remains the most cited challenge, further eforts
should focus on overcoming this barrier to evidence access.</p>
      <p>This research is vital for forensic investigators aiming to collect more evidence and solve more crimes.
As society digitizes, the importance of addressing digital forensic challenges will only grow.</p>
    </sec>
    <sec id="sec-8">
      <title>Declaration on Generative AI</title>
      <p>During the preparation of this work, the authors used ChatGPT-4 and Grammarly in order to check
grammar and spelling. After using these tools, the authors reviewed and edited the content as needed
and takes full responsibility for the publication’s content.
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. . .
. . .
. . .</p>
      <sec id="sec-8-1">
        <title>Text with Sub-theme and Theme</title>
        <p>. . .</p>
        <p>Most of the mobile forensic tools do not support or do not have
capabilities that can enable integration of application artifacts with known
encodings like PDF or MS-Word.</p>
        <p>Sub-theme: Forensic Tool Challenges; Theme: Technical Challenges
Furthermore, to secure user data, Windows smartphone devices contain
encryption and security features such as device encryption and user
authentication. However, these security procedures may obstruct data
extraction and analysis throughout the forensic process.
Sub-theme: Data Protection and Anti-Forensics, Security; Theme:
Anti-Forensics Challenges
With new and innovative technology entering the market every few
weeks, digital forensic investigators have to continuously learn and
update their current knowledge and skills on how to digitally
investigate these devices.</p>
        <p>Sub-theme: Technological Evolution; Theme: Technical Challenges
The proposed methodology also shows that there are significant
differences between rooted and unrooted devices for data acquisition.
Sub-theme: Evidence acquisition; Theme: Technical Challenges
Also, efective data erasing functions at the OS level make it dificult
to find data remnants in physical data.</p>
        <p>Sub-theme: Data Protection and Anti-Forensics; Theme:
AntiForensics Challenges
Unfortunately, there is not yet a standardised method for gathering
data from these devices that may be relevant to scientists.
Sub-theme: Method; Theme: Methodological and Development
Challenges
. . .</p>
      </sec>
    </sec>
  </body>
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