Strategies to preve nt OVERINFLATION A CONVERSATION for Judges Prosecutors and Defense Attorneys November 2 2023 Matthew B Howard Assistant District Attorney Director OF THE Conviction Integrity Unit ID: 1045558
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1. Presenting Forensic DNA Evidence to Juries:Strategies to prevent OVERINFLATIONA CONVERSATION for Judges, Prosecutors, and Defense AttorneysNovember 2, 2023Matthew B. HowardAssistant District AttorneyDirector OF THE Conviction Integrity UnitBexar County Criminal District Attorney’s Office
2. Sales, Not Warranties
3. Importance of Avoiding OverinflationPresenting DNA evidence carries a risk of overinflating its importance in the eyes of the jury.Overinflation can lead to undue weight being placed on the DNA evidence, potentially overshadowing other crucial aspects of the case.Attorneys should strive for a balanced and objective presentation of DNA evidence to avoid prejudicing the jury's perception.
4. Pre-Trial ConsiderationsEarly consultation with DNA experts is essential to understand the evidence and its limitations.Relevant education, training, and experience in DNA analysisQualifications, Expertise, and LimitationsThe defense should have access to the prosecution's DNA expert reports and access to independent experts if necessary.The prosecution must disclose all relevant DNA evidence and any potential issues or challenges.
5. The Daubert standardBe prepared to discuss the method and validation of the methodBe open and honest about error rates, issues, and blind-spotsPeer Review and Publication
6. DNA ContaminationAsk the hard questions:Was there a risk of contamination during:Evidence collection?Evidence handling?Evidence analysis?What protocols are in place to prevent contamination?Highlight quality controls, laboratory procedures, and chain of custody documentation
7. Striking a balance:Discussing Statistical InterpretationClear communication of statistical results is key – consider balance between simplifying the findings and over simplifying the findings.Be familiar with Statistical Methods (Random Match Probability vs. Likelihood Ratio) and the distinction between the two. Have a conversation with your expert, in front of the jury, about challenges and realistic terms – try to avoid overwhelming the jury with technical jargon and focus on the key findings.
8. Striking a balance:Discussing Statistical InterpretationExample:Q: Can you explain the challenges involved with interpreting DNA mixtures, where DNA from multiple contributors is present? vs.Q: Can you walk us through what you mean when you say, “DNA mixture”?
9. Strategies to Prevent Overinflation:Direct ExaminationPrepare the expert to explain their analysis, methodology, and results in a clear and accessible mannerContextualize DNA Evidence, but don’t misuse your expert
10. Strategies to Prevent Overinflation:Direct ExaminationDo:Explain the science behind DNA analysis and its limitations.Clearly communicate the probabilistic nature of DNA evidence and the potential for errors or contamination.Don’t:Use direct to make your argument about the overview of the case, or to push the facts(You can highlight the significance of DNA evidence within the broader context later – paint that picture in argument!)
11. Strategies to Prevent Overinflation:Cross Examination Considerations“Know enough to be dangerous”Question the MethodologyHighlight Potential Contamination or Sample Mix-upAddress Error Rates and Statistical Interpretation Issues
12. Strategies to Prevent Overinflation:Cross Examination Considerations“Know enough to be dangerous”Review the DNA Report and look for remarks, issues with the evidenceConsult with Your Own DNA Expert and ask about potential issues with these methods
13. Strategies to Prevent Overinflation:ARGUMENT TO THE JURYThis is the time to highlight the significance of DNA evidence within the broader context – paint the big pictureUse clear and accurate closing argument regarding DNA evidence – avoid “basically” or “essentially” or “might as well have said”sOwn the meaning and limitations for the jury – or risk that opposing counsel will do it for you
14. Sales, Not WarrantiesReally boils down to “be ethical, don’t be unethical”
15. Thank you!Matthew B. HowardMatthew.Howard@bexar.org(210) 335-2418