The Digital Forensic Investigation Lifecycle

Digital Forensic Investigation Lifecycle
Field	Digital forensics
Core phases (INTERPOL)	Acquisition → Extraction → Analysis → Reporting
Core phases (Maras, 2014)	Search/identification → Description → Examination → Reporting
Governing standard	ISO/IEC 27043:2015
Concurrent processes	Authorization, documentation, chain of custody
Related	Digital Forensics, Chain of Custody

The digital forensic investigation lifecycle is the sequence of stages by which an examiner moves from a seized or acquired digital device to a finished, legally defensible account of what that device contains and what it shows. Although individual authors and standards bodies have proposed dozens of variant process models since the mid-1990s, most converge on the same underlying structure: evidence is first captured in a forensically sound way, meaningful data is then pulled out of that captured copy, the extracted data is interpreted in light of the investigation's questions, and the results are written up for use in a case or in court. This article surveys the two most commonly cited formulations of that structure — Marie-Helen Maras's four-stage definition and INTERPOL's four-phase operational model — before turning to the technical requirement of forensic imaging, the 2015 harmonized process model of Valjarevic and Venter, the concept of digital forensic readiness, and the international standard, ISO/IEC 27043:2015, that ties these ideas together.^[1]

The lifecycle described here is the connective tissue behind the more general discussion in Digital Forensics, and it depends throughout on the evidentiary safeguards discussed in Chain of Custody and on the institutional standards catalogued in International Forensic Standards.

1 Maras's four-stage definition

One of the most widely cited compact definitions of digital forensics comes from Marie-Helen Maras, a professor at John Jay College of Criminal Justice (CUNY), in Computer Forensics: Cybercriminals, Laws, and Evidence (2nd ed., 2014). Maras frames the discipline as consisting of four stages:^[2]

1. Search and identification of digital evidence — locating the devices, accounts, and media that may hold data relevant to the matter under investigation;
2. Description of that evidence — recording what was found, where, and in what condition, so the item can later be identified unambiguously;
3. Examination — assessing the evidence's reliability, validity, and relevance to the case; and
4. Reporting of the evidence — documenting findings in a form usable by investigators, attorneys, or a court.

Maras's definition is deliberately compact and is widely reproduced in law-enforcement training curricula, including anti-trafficking digital-forensics training material used across the European Union. Its distinguishing feature relative to other models is the explicit separation of description from examination: an item can be accurately described (what it is, where it was found) well before an examiner has formed any view about whether it is reliable or relevant, and Maras's model insists that these are analytically separate steps rather than a single "collect and analyze" motion.

2 INTERPOL's four-phase model

INTERPOL's Global Guidelines for Digital Forensics Laboratories, issued from its digital forensics laboratory in Lyon and aimed at supporting forensic capability across its 194-plus member countries, converges on a structurally similar but differently labeled four-phase model:^[3]

1. Acquisition — forensically sound imaging or capture of the source device or media;
2. Extraction — recovering data and artifacts from the acquired evidence;
3. Analysis — interpreting the extracted data in the context of the investigation; and
4. Reporting — preparing findings for use in an investigation or a court proceeding.

The mapping onto Maras's terminology is close but not exact. INTERPOL's acquisition phase corresponds to Maras's search and identification plus the act of imaging; extraction is a technical step — pulling files, artifacts, and metadata out of a forensic image — that sits between Maras's description and examination; and analysis and reporting map directly onto Maras's examination and reporting. Because INTERPOL's guidelines are written for laboratory operations rather than as an academic definition, they also cover matters outside the four-phase model itself — laboratory premises and physical security, staffing, required examiner competencies, and recommended hardware and software — with the explicit institutional goal of closing the digital-forensics capacity gap between wealthier and less-resourced member states.

Dubey, Bhatt, and Negi's 2023 review of digital forensics techniques and trends independently converges on the same three-part backbone — acquisition, analysis, and presentation — describing it as the standard process by which digital evidence is uncovered, validated, and interpreted in cases spanning intellectual property theft, fraud, data theft, bankruptcy investigation, forgery, and industrial espionage.^[4]

3 Forensic imaging and hash verification

Whichever labeling scheme is used, the acquisition or search-and-identification stage rests on a single non-negotiable technical requirement: the original evidence must never be examined directly. Instead, an examiner creates a forensic image — a bit-for-bit copy of the source media, capturing every sector rather than only the visible file system — and all subsequent extraction and analysis is performed on that copy. Direct testing on original media is considered forensically improper because it risks altering the very evidence under examination and undermines the claim, essential to admissibility, that the material presented in court is identical to what was seized.^[4]

To prove that the image is an exact, unaltered copy, examiners compute a cryptographic hash — typically an MD5 checksum, a SHA-1, or a stronger SHA-2 family hash — of the source media before imaging and of the resulting image after imaging. If the two hash values match, the copy is verified as identical to the original; if the source media is later re-examined or the image is duplicated again, the same hash values should reproduce, giving a durable, mathematically verifiable proof of integrity that supports the chain-of-custody record described in Chain of Custody. This hash-verification step is the technical mechanism that makes the higher-level admissibility properties discussed in Section 7 below — auditability, repeatability, reproducibility — concrete rather than aspirational.

Dubey, Bhatt, and Negi's review also stresses that, for legal admissibility, investigations should be conducted live, recorded, and independently verified by multiple teams where feasible — an operational echo of the blind-verification safeguards discussed elsewhere in the wiki's forensic-validity literature, and a direct response to the risk that a single examiner's unchecked conclusion becomes the entire evidentiary record.

4 The harmonized process model of Valjarevic and Venter

Prior to the mid-2010s, the digital forensics field had accumulated a large and inconsistent set of competing process models, varying in the number of stages, their scope, their hierarchical structure, and their terminology — a proliferation that undermined consistency and legal defensibility across jurisdictions. Aleksandar Valjarevic and Hein S. Venter addressed this directly in "A Comprehensive and Harmonized Digital Forensic Investigation Process Model" (Journal of Forensic Sciences 60(6), 2015), which synthesized the existing literature into a single unified structure rather than proposing yet another competing model from scratch.^[5]

Two contributions of the harmonized model stand out as extensions beyond the simpler four-stage formulations above:

• It formally incorporates digital forensic readiness as a distinct, proactive process class that precedes any incident, rather than treating investigation as something that only begins once a device has already been seized.
• It introduces the concept of concurrent processes — activities that run in parallel across multiple sequential stages rather than being confined to a single phase.

Both concepts are discussed in their own right below because they represent the most significant structural addition the harmonized model makes to the simpler acquisition-extraction-analysis-reporting sequence, and because both are subsequently reflected in the international standard discussed in Section 7.

5 Digital forensic readiness

Digital forensic readiness (DFR) is an organization's proactive capability to maximize its ability to collect credible digital evidence, while minimizing the cost and disruption of any subsequent investigation, achieved through advance planning rather than improvisation after the fact. Concretely, DFR includes measures such as logging policies that ensure relevant system and application activity is actually recorded before it is needed, staff training so that personnel do not destroy or contaminate evidence when an incident is first discovered, and pre-established incident-response procedures that specify who is authorized to act and how evidence is to be preserved from the first moment of suspicion.^[5]

DFR is significant because it reframes digital forensics as something an organization builds capacity for continuously, rather than a service it calls in only after a breach or a fraud is suspected. An organization with strong logging, clear documentation practices, and rehearsed evidence-preservation procedures will produce a far more complete and legally defensible evidentiary record than one that begins improvising chain-of-custody documentation only once an incident has already been detected. This mirrors a theme that recurs throughout fraud-examination literature more broadly: organizations that build controls and documentation into normal operations, rather than relying on after-the-fact reconstruction, are consistently better positioned both to detect wrongdoing and to prove what happened once it is found.

6 Concurrent processes

The second major structural contribution of the harmonized model is the idea that certain activities are not confined to a single stage of the lifecycle but instead run concurrently, in parallel, across some or all of the sequential stages described above. Valjarevic and Venter identify three such concurrent processes as central to the harmonized model:^[5]

• Authorization — obtaining and documenting the legal or organizational authority to acquire, extract, and analyze evidence, which must be established before acquisition begins and may need to be revisited or extended as an investigation's scope evolves;
• Documentation — the continuous, contemporaneous record of every action taken, by whom, and why, spanning from initial identification of a device through final reporting; and
• Chain of custody — the unbroken record of who has possessed and handled the evidence at every point, which must be maintained from the moment of acquisition and cannot be reconstructed retroactively without weakening its evidentiary value (see Chain of Custody).

Treating these as concurrent rather than sequential processes is intended to make investigations more efficient — an examiner does not have to pause the substantive work of extraction or analysis to "do documentation" as a separate step, because documentation is happening throughout — while simultaneously strengthening evidentiary admissibility, since a documentation and custody trail built continuously alongside the technical work is harder to challenge than one assembled afterward from memory or incomplete notes.

7 ISO/IEC 27043:2015

ISO/IEC 27043:2015, Information technology — Security techniques — Incident investigation principles and processes, is the international standard most closely aligned with the harmonized process model described above; Valjarevic and Venter's own work on process harmonization is closely tied to this standard. It is part of the broader ISO/IEC 27000 family of information-security standards, which elsewhere includes ISO/IEC 27037:2012 (covering identification, collection, acquisition, and preservation of digital evidence) and ISO/IEC 27042:2015 (covering the analysis and interpretation phases specifically).^[6]

ISO/IEC 27043:2015 provides guidance intended to ensure that a digital investigation, regardless of which specific incident type prompted it, is conducted with the properties needed for its results to withstand legal and technical scrutiny: sufficient recording of process detail that another qualified examiner could independently review or reproduce the work, and a structure broad enough to accommodate readiness activities and concurrent processes rather than treating an investigation as a rigid, strictly sequential checklist. Its scope deliberately spans the full incident-investigation lifecycle — including the pre-incident readiness activities discussed in Section 5 — rather than beginning only at the point of evidence acquisition, which is precisely the harmonization Valjarevic and Venter's academic model set out to achieve.

8 Why the models converge

Despite differing vocabulary — Maras's search/identification, description, examination, reporting versus INTERPOL's acquisition, extraction, analysis, reporting versus Dubey, Bhatt, and Negi's acquisition, analysis, presentation — every formulation surveyed in this article shares the same underlying logic: capture evidence soundly before touching it substantively, pull out what is relevant, interpret it in context, and communicate the result in a form that can survive challenge. The harmonized model's two additions, digital forensic readiness and concurrent processes, do not compete with this basic sequence; they extend it backward in time (readiness, before any incident occurs) and thread additional obligations through it (authorization, documentation, and custody, running alongside every stage rather than confined to one). ISO/IEC 27043:2015 then supplies the formal international reference point that ties the academic harmonization effort to a standard laboratories and courts can cite directly, complementing the laboratory-operations guidance in INTERPOL's own global guidelines and the broader standards landscape catalogued in International Forensic Standards.

See also: Digital Forensics, Chain of Custody, International Forensic Standards, Evidence and Testimony.

References

1. Valjarevic, A. & Venter, H. S. "A Comprehensive and Harmonized Digital Forensic Investigation Process Model." Journal of Forensic Sciences 60(6), 2015, pp. 1467-1483. DOI: 10.1111/1556-4029.12823.
2. Maras, M.-H. Computer Forensics: Cybercriminals, Laws, and Evidence (2nd ed.). Jones & Bartlett Learning, 2014. ISBN 978-1449692223.
3. INTERPOL Digital Forensics Laboratory. "Global Guidelines for Digital Forensics Laboratories." INTERPOL, Lyon. https://www.interpol.int/content/download/13501/file/INTERPOL_DFL_GlobalGuidelinesDigitalForensics
4. Dubey, H., Bhatt, S., & Negi, L. "Digital Forensics Techniques and Trends: A Review." International Arab Journal of Information Technology 20(4), 2023, pp. 644-654. DOI: 10.34028/iajit/20/4/11.
5. Valjarevic, A. & Venter, H. S. (2015), as above — digital forensic readiness and concurrent-processes discussion.
6. International Organization for Standardization / International Electrotechnical Commission. ISO/IEC 27043:2015, "Incident investigation principles and processes." https://www.iso.org/standard/44407.html