Forensic DNA and Biology Expert Witnesses

• Short tandem repeat (STR) analysis using capillary electrophoresis
• Body-fluid identification and serology (presumptive and confirmatory testing)
• DNA extraction, quantification, and amplification (PCR)
• Mixture deconvolution and interpretation of multi-contributor samples
• Probabilistic genotyping software interpretation (for example STRmix, TrueAllele) and likelihood-ratio weighting
• Low-template and touch DNA analysis, with attention to transfer and contamination
• Y-STR and mitochondrial DNA analysis for degraded, limited, or lineage samples
• Kinship and relationship analysis

• Bench experience versus review-only. Confirm whether the expert has personally performed extraction, typing, and interpretation on a validated platform, or has only reviewed casework. Both have a place, but the distinction matters for cross-examination.
• Currency with mixture and probabilistic methods. Verify recent, hands-on familiarity with the probabilistic genotyping software at issue in your matter. Interpretation standards have shifted materially, and older-generation training may not cover current mixture practice.
• Laboratory accreditation and standards followed. Ask which accreditation body oversaw the labs the expert worked in and which validation and interpretation guidelines they follow. Confirm the specific claims independently rather than relying on the CV.
• Prior testimony and any exclusions. Request a testimony list and ask directly whether the expert's opinions have ever been limited or excluded by a court, and on what grounds.
• Independence and disclosure of conflicts. Confirm the expert has no prior involvement with the evidence, laboratory, or parties that would create a conflict or the appearance of one.
• Report and case throughput. Understand current caseload and turnaround, since bench re-analysis and software runs take time and a thin schedule can miss your deadlines.

1. Describe your hands-on experience performing STR analysis and mixture interpretation, as distinct from case review, and when you last did each.
2. Which probabilistic genotyping systems have you used, on how many cases, and are you prepared to be examined on their validation and assumptions?
3. What accreditation and interpretation standards governed the laboratories where you performed or oversaw casework?
4. Have any of your opinions been limited, excluded, or the subject of a Daubert or Frye challenge, and what was the outcome?
5. How do you address low-template or touch DNA, including the risks of transfer, secondary transfer, and contamination?
6. Will you conduct independent re-analysis, review existing data and reports, or both, and what materials do you require from us?
7. What is your realistic timeline for a written report and your current availability for deposition and trial?
8. How do you state the strength of a DNA result, and how do you explain the difference between a match statistic and any conclusion about how or when DNA was deposited?

• States or implies that a DNA match identifies who committed an act or when DNA was deposited, rather than confining opinions to the profile and its statistical weight
• Claims certainty or overstates a match statistic instead of expressing results as a likelihood ratio or random match probability
• Is unfamiliar with the probabilistic genotyping software or mixture methods at issue, yet offers opinions on those results
• Cannot identify the accreditation or interpretation standards used by the laboratories in their background
• Refuses to provide a testimony history or is evasive about prior exclusions or challenges
• Offers opinions well outside DNA and biology, such as bloodstain pattern conclusions or cause-of-death opinions, without the corresponding qualifications

Bodies referenced in this discipline. Listed for context; they do not endorse this index or any provider. Verify any credential directly with the issuing body.

SWGDAM

Scientific Working Group on DNA Analysis Methods. Issues interpretation and validation guidelines widely referenced in US forensic DNA practice.

ABC

American Board of Criminalistics. Offers certification for forensic scientists, including molecular biology and forensic biology disciplines.

ANAB

ANSI National Accreditation Board. Accredits forensic testing laboratories to international standards; useful for checking a lab's accreditation.

AAFS

American Academy of Forensic Sciences. Professional membership body spanning forensic disciplines, including a criminalistics section.

NIST

National Institute of Standards and Technology. Develops reference materials and technical guidance relevant to DNA measurement and interpretation.

ISFG

International Society for Forensic Genetics. Publishes internationally recognized recommendations on DNA mixture interpretation and biostatistics.