Quick Answer
The answer is Locard's exchange principle, the foundational forensic concept stating that every contact leaves a trace. This principle is correct because it asserts that whenever two objects interact, there is a mutual transfer of material; in digital forensics, this means any digital activity—such as opening a file, sending a network packet, or logging into a system—inevitably leaves residual evidence in logs, memory dumps, registry entries, or file metadata. On the Computer Hacking Forensic Investigator CHFI exam, this principle tests your understanding that digital evidence recovery relies on the inevitability of trace evidence, often appearing in questions about data persistence or anti-forensics countermeasures. A common trap is confusing it with the concept of "volatility" or "order of volatility," but remember: Locard’s principle is about the *existence* of traces, not their stability. Memory tip: think "every touch leaves a trace"—if a suspect touched a system digitally, the system holds a record.
This CHFI practice question tests your understanding of computer forensics fundamentals and process. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which principle states that every contact leaves a trace?
Locard's exchange principle
Correct. This principle is fundamental in forensic science.
Chain of custody
Why wrong: Chain of custody is the documentation of evidence handling.
Best evidence rule
Why wrong: The best evidence rule requires original evidence rather than copies.
Hearsay rule
Why wrong: Hearsay is an out-of-court statement offered for the truth of the matter.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Locard's exchange principle
Locard's exchange principle is the foundational forensic concept stating that whenever two objects come into contact, there is a transfer of material between them. In computer forensics, this means that digital activity—such as accessing a file, sending a packet, or connecting to a network—inevitably leaves traces in logs, memory, registry entries, or file metadata. This principle underpins the entire discipline of digital evidence recovery.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Locard's exchange principle
Why this is correct
Correct. This principle is fundamental in forensic science.
Related concept
Read the scenario before looking for a memorised answer.
Chain of custody
Why it's wrong here
Chain of custody is the documentation of evidence handling.
Best evidence rule
Why it's wrong here
The best evidence rule requires original evidence rather than copies.
Hearsay rule
Why it's wrong here
Hearsay is an out-of-court statement offered for the truth of the matter.
Common exam traps
EC-Council often tests the distinction between a forensic principle (Locard's) and legal or procedural rules (chain of custody, best evidence, hearsay), so candidates mistakenly select a legal term that sounds related to evidence handling rather than the core scientific concept.
Detailed technical explanation
Under the hood, Locard's principle manifests in digital forensics through artifacts like TCP/IP packet headers (which contain source/destination IPs and timestamps), file system journal entries (e.g., NTFS $LogFile or ext3 journal), and volatile memory artifacts (e.g., network connections in /proc/net/tcp on Linux). A real-world scenario: a suspect connects a USB drive to a Windows system; the USBSTOR registry key, setupapi.dev.log, and $MFT timestamps all record the event, even if the user deletes files—demonstrating that contact always leaves a trace.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the CHFI exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Computer Forensics Fundamentals and Process — This question tests Computer Forensics Fundamentals and Process — Read the scenario before looking for a memorised answer..
The correct answer is: Locard's exchange principle — Locard's exchange principle is the foundational forensic concept stating that whenever two objects come into contact, there is a transfer of material between them. In computer forensics, this means that digital activity—such as accessing a file, sending a packet, or connecting to a network—inevitably leaves traces in logs, memory, registry entries, or file metadata. This principle underpins the entire discipline of digital evidence recovery.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This CHFI practice question is part of Courseiva's free EC-Council certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CHFI exam.
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