Criminal Defense: Excluding Prosecution Digital Evidence Through Forensic Rebuttal
The Challenge
Client charged with distribution of child exploitation materials based on prosecution forensic evidence claiming defendant's computer contained 400+ illegal images and peer-to-peer file sharing software. Prosecution expert testified files were "knowingly downloaded and shared." Defense needed independent forensic examination to challenge evidence admissibility and rebut prosecution conclusions.
Our Approach
Independent forensic examination of original evidence (not prosecution-processed copies) to verify findings
Chain of custody analysis identifying multiple gaps and improper evidence handling by law enforcement
Tool validation testing revealing prosecution used outdated forensic software with known false positive rates
Malware analysis discovering active peer-to-peer infection that autonomously downloaded files without user knowledge
Timeline analysis proving many files arrived during periods when defendant provably not at computer (work, documented travel)
Hash value comparison with NIST NSRL database showing many "illegal images" were actually hash collisions with benign files
Internet history analysis showing no evidence of intentional seeking or accessing prohibited content
File allocation analysis revealing files in unallocated space (automatically cached, never user-accessed)
Expert rebuttal report identifying methodology flaws in prosecution's forensic examination
Daubert challenge to prosecution expert's qualifications and reliability of methods
Key Forensic Findings
Chain of custody showed 3-week gap where evidence custody undocumented and stored in unlocked office
Prosecution forensic tool (EnCase 5.0) was 8 versions outdated with documented false positive issues
Malware analysis identified LimeWire P2P infection automatically downloading files to shared folder without user interaction
Timeline showed 147 files arrived during documented periods when defendant at work or traveling (cell phone GPS, work badge swipes)
Hash analysis revealed 89 flagged images were false positives (hash matched NSRL benign file database)
File system analysis proved 312 files in unallocated space - browser cache files never intentionally accessed
Internet history showed ZERO searches or intentional access to illegal content websites
Forensic report documented prosecution expert made 14 methodology errors violating NIST SP 800-86 guidelines
Expert demonstrated prosecution's "knowingly shared" conclusion scientifically unsupported - malware auto-sharing, not user action
The Outcome
Court excluded prosecution's forensic evidence after Daubert hearing, finding methodology unreliable and chain of custody fatally flawed. Rebuttal expert testimony demonstrated: (1) Malware infection, not user action, downloaded files; (2) Defendant never accessed the files; (3) Prosecution's forensic tool generated false positives; (4) Chain of custody violations compromised evidence integrity. Prosecution dismissed all charges after losing forensic evidence. Client vindicated after 14 months of proceedings.
Case Impact
Services Utilized
Independent Forensic Examination
Chain of Custody Analysis
Malware Analysis
Timeline Reconstruction
Tool Validation Testing
Expert Rebuttal Reports
Daubert Challenge Support
Criminal Defense Expert Testimony