Challenging Forensic Evidence in Sexual Offence Cases – A Detailed Defence Strategy
Challenging Forensic Evidence in Sexual Offence Cases – A Detailed Defence Strategy
Challenging forensic evidence in sexual offence cases is often essential, as material such as DNA, bodily fluids, or clothing fibres is frequently presented as irrefutable in court. In reality, it can be incomplete, misinterpreted, or even misleading.
At Makwanas, we have defended clients where flawed forensic evidence was the main basis of the prosecution case — and by exposing those flaws, we have secured acquittals.
Book Your Free Discovery Call Today – Get expert advice on contesting forensic evidence.
Types of Forensic Evidence in Sexual Offence Cases
- DNA Profiles – Bodily fluids, skin cells, hair.
- Bodily Fluid Analysis – Semen, saliva, blood.
- Injury Analysis – Bruises, cuts, or marks interpreted as evidence of assault.
- Material Transfer – Clothing fibres, soil, or other particles linking individuals or locations.
Common Weaknesses in Forensic Evidence
- Collection Errors
Failure to follow sterile procedures.
Evidence gathered outside recommended timeframes. - Chain of Custody Issues
Incomplete logs of who handled the evidence and when. - Laboratory Mistakes
Cross-contamination.
Mislabelled samples.
Inaccurate or unverified analysis. - Overinterpretation of Results
DNA presence does not prove time, location, or consent.
Injury patterns can have multiple explanations.
Defence Approaches to Challenging Forensic Evidence
- Independent Expert Analysis – Re-testing samples or reviewing lab methods.
- Alternative Explanations – Demonstrating how DNA transfer could have occurred innocently.
- Procedural Challenges – Proving breaches in collection or storage protocols.
- Contextual Evidence – Showing how other case facts undermine forensic conclusions.
Why Forensic Evidence Alone Rarely Tells the Whole Story
- DNA can survive on surfaces for days or weeks.
- Trace transfer can happen through shared objects or indirect contact.
- Clothing fibres may transfer in social, non-criminal interactions.
FAQs: Challenging Forensic Evidence in Sexual Offence Cases
1. Can DNA evidence be wrong?
Yes — contamination, mishandling, or incorrect interpretation can lead to errors.
2. Can I get my own forensic test?
Yes — the defence can instruct independent experts.
3. Does finding my DNA prove I committed the offence?
No — it only proves transfer, not intent or consent.
4. How often is forensic evidence excluded?
More than you might think, particularly when procedures are breached.
5. Can forensic evidence help the defence?
Yes — it can support your version of events if tested and interpreted correctly.
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