How To Better Screen for Male DNA in Sexual Assault Samples

Summary

The video discusses the challenges forensic laboratories face with sexual assault case samples, which often involve small quantities of male DNA or complex mixtures. It highlights an efficient workflow using the Quantifiler™ REO kit for DNA quantification, enabling rapid identification of male DNA presence. The process is demonstrated through two case examples, showing how the kit aids in triaging samples and determining the appropriate DNA analysis strategy. The use of the Y-filer™ Plus kit is also explored, providing insights into successful male DNA profiling even with overwhelming female DNA, ensuring optimal analysis for sexual assault cases.

Takeaways

• 😀 35% of women worldwide have experienced intimate partner violence or non-partner sexual violence in their lifetime.
• 😀 In the U.S., over 293,000 people are victims of rape or sexual assault every year, equivalent to one victim every two minutes.
• 😀 Forensic laboratories face challenges with sexual assault samples due to low male DNA and complex DNA mixtures.
• 😀 DNA profiling in sexual assault cases is labor-intensive and time-consuming, especially with complex mixtures.
• 😀 The Quantifier Alert REO Kit can accurately detect sub-picogram levels of DNA, helping forensic labs confirm the presence of male DNA in sexual assault samples.
• 😀 The Quantifier Alert REO Kit allows labs to process up to 20 sexual assault kits in under two hours, improving workflow efficiency.
• 😀 The process involves cutting a small sample from a cotton swab, lysing sperm cells, and then performing real-time PCR to detect male DNA.
• 😀 Differential extraction is used to isolate male DNA from female DNA in sexual assault samples, which helps with accurate analysis.
• 😀 The Quantifier Trio Kit helps identify the male-to-female DNA ratio, guiding STR analysis and sample strategy decisions.
• 😀 The Y-Filer Plus Kit, a multiplex Y-STR kit, allows for amplification of male DNA even in samples with a high female DNA presence, ensuring a clear male DNA profile.
• 😀 The initial male DNA concentration can be as low as 0.07 nanograms per microliter, and the Y-Filer Plus Kit still provides a full male profile without artifacts, even in challenging cases.

Q & A

What is the global statistic regarding intimate partner violence or non-partner sexual violence experienced by women?

Recent global figures indicate that 35% of women worldwide have experienced either intimate partner violence or non-partner sexual violence in their lifetime.

How many people in the U.S. are victims of rape or sexual assault each year?

In the U.S., over 293,000 people are victims of rape or sexual assault annually, which is equivalent to one victim every two minutes.

Why are samples from sexual assault cases difficult to analyze in forensic laboratories?

Samples from sexual assault cases are challenging because they often have a very small quantity of male DNA compared to a high quantity of female DNA, or they contain multiple male contributors, making mixture analysis complex.

What are the challenges involved in achieving a DNA profile from sexual assault samples?

The steps to achieve a DNA profile from sexual assault samples are labor-intensive and time-consuming, adding to the complexity of the analysis.

What is the role of the Quantifier Trio kit in sexual assault case work?

The Quantifier Trio kit is used for DNA quantification in sexual assault case work. It can detect sub-picogram levels of DNA and accurately confirm the presence or absence of male DNA in a sample in less than two hours.

How does the Quantifier Trio kit help in deciding the viability of a sexual assault sample for further processing?

By using the Quantifier Trio kit, forensic scientists can determine if there is male DNA in the sample and decide whether the sample is viable for further processing, such as differential extraction.

What does the quantification result from the Quantifier Trio kit tell us in the case of a sperm fraction sample?

The quantification result from the Quantifier Trio kit shows the total DNA quantity and the male DNA content. For instance, in the case of a sperm fraction sample, a male concentration of 6 picograms per microliter was detected, allowing for a successful male DNA profile amplification.

Why might a typical autosomal amplification kit fail to detect male DNA in certain sexual assault samples?

A typical autosomal amplification kit might fail because it is overwhelmed by female DNA in cases where the male DNA is present in very small amounts, as seen in samples with a male-to-female DNA ratio of 1 to 1498.

What is the purpose of the Y-Filer Plus kit in the context of sexual assault cases?

The Y-Filer Plus kit is used for cases with low male DNA content, as it is designed to amplify Y-chromosome STR markers. This kit allows for the detection of male DNA even in samples with a high female DNA presence.

What advantage does the Y-Filer Plus kit provide in cases with a high amount of female DNA?

The Y-Filer Plus kit allows for the successful amplification of male DNA profiles even when a large amount of female DNA is present, ensuring a complete and accurate male profile without interference from the female DNA.