moot court preparation

Please state your name

Janiyah Turner

What is your educational background

I received a bachelor’s degree in forensic science with a concentration in biology from Western Carolina University

Where do you work

The Catamount Crime Lab

How many cases have you worked

6

How many times have you testified

2

Can you describe the evidence that you processed for this case?

The evidence that we had in this case were a pair of white Amazon essential women’s underwear, which were size medium. The underwear had a visible dark red-ish brown mark on the gusset of the underwear.

Did you confirm that the chain of custody was maintained? How do you know?

Yes we did. Before we are able to examine the evidence, we obtain it from the Catamount evidence locker. The evidence was in a paper evidence bag and sealed with evidence tap. The person who collected evidence has signed the evidence bag prior to us getting it, and we signed it out when we began our examination.

Explain how you handled the evidence after first opening

Prior to even thinking about opening up the evidence from its paper bag, we must be in appropriate PPE and have sterile and clean instruments.

What biological fluids were present on the evidence? How did you come to this conclusion?

On the underwear we located a potential blood stain on the gusset and a potential semen stain on the gusset

We were able to perform preliminary and confirmatory tests on these stains to confirm the identification of the biological fluid

Can you explain how the RSID test works? What would you do if the test control line didn’t perform as expected?

RSID test stands for Rapid Stain Identification test, is similar to a COVID test

Explain the general process for DNA analysis.

DNA analysis has 5 steps:

Cells are collected and disrupted to release and isolate small amounts of DNA

DNA is quantified

Multiple STR regions of DNA are amplified by PCR

PCR products are sized using capillary electrophoresis

Pattern of fragment distribution is analyzed/compared

What is your laboratory criteria for stating that you have a “match” between a Q and a K?

In order for you to have a match between your questioned or Q samples and your known or K samples, the profiles would have to match up at every location without ANY differences at all.

I noticed that you included a K sample from you and your lab partner. Why did you do this?

We included a K or known sample from myself and my lab partner so that we would have a reference in case we viewed any contamination in our Q or questioned samples.

Can you explain what DNA is to a lay audience?

DNA is the molecule that carries genetic information

Can you define basic terms like locus and allele?

Locus - a specific location on a chromosome where a particular gene or genetic marker is located

Allele - a different form or variation of a gene or genetic marker at a particular locus

Does the serological test affect the DNA in the sample?

No

What DNA extraction kit was used? How does the kit work?

The Qiagen QIAmp DNA Investigator kit

It is a silica-based solid phase method

• Lyse open cells

• Bind DNA

• wash

• Elute

Buffer contains

• SDS which disrupts cell membranes

• EDTA chelate metal cations

• Proteinase K helps digest proteins

• DTT helps break up disulfide bonds

Why do you use qPCR? How is it different from end-point PCR?

Quantitative PCR or real-time PCR helps us see how much DNA we were able to extract from our samples

End-point PCR focuses on amplifying DNA

Why do you use the small autosomal target for quantitation? What is the point of including the large autosomal target?

We chose to use the small autosomal target for quantitation since it is the primary quant target for the human genome & can be used to detect DNA that may be slightly degraded.

The large autosomal target is primarily used to indicate degradation

How can you use qPCR(real time) to detect the presence of an inhibitor in your sample?

With qPCR you can use an internal positive control, which is synthetic DNA template, which helps you make sure that all components of the assay are performing properly

If there are no inhibitors then the IPC when perform as expected

If there are inhibitors the IPC and sample show less amplification

What is inhibition? What are common inhibitors encountered in the forensic laboratory?

Inhibition is a process where the polymerase chain reaction has been affected

Heme - blood

Indigo dyes - denim

Urea - urine

Melanin - hair

How can you use qPCR to assess degradation in your sample?

qPCR can assess degradation by looking at your small and large autosomal targets (small over large)

Based on your qPCR results, did you have to perform dilutions of your samples prior to PCR?

no

Can you describe what STRs are and why they are used in forensic profiling?

STRs stand for short tandem repeats

1-5bp

High heterozygosity

Can you describe your STR results? Did you have single source profiles? Mixtures? What indicators do you look for in each case?

Single source profiles, there were no more than 2 peaks located at a single locus

What sex determining markers are included in the GlobalFiler kit? What would you expect the results for the amelogenin locus to look like if the sample donor were a biological male?

Amelogenin, Y-specific DYS391 and Y-indel

For amelogenin you can either have one X peak, meaning that it would be a woman & for a man you would see an X and Y peak

Can you describe the controls you used when processing the evidence in question? What were your results?

Positive control, reagent blanks, and NTC

Positive control had external contamination but worked as expected

Reagent blank 2 worked as expected

NTC had contaminations that was traced back to one of our analysts

What thresholds does your lab use for STR analysis? Can you describe them? What would you do if an allele fell between the analytical and stochastic threshold?

Analytical threshold is the minimum peak height that the peaks much reach to be distinguished from the machine background noise

Stochastic threshold is the minimum peak height that all peaks at a locus must be to confidently state that no allele drop out has occurred

We used the standard threshold which was 100 and 250

Artifacts – Was there evidence of stutter in your Q electropherograms? What does that mean? What about split peaks? Ski slope effect?

There were no artifacts in our questioned profile

What is CE? How does it work?

CE stands for capillary electrophoresis

We use an automated instrument that allows us to separate PCR fragments by size based on charge, the smaller fragments move through the capillaries quicker than the larger ones

DNA is loaded at negative end and when

How are unknown PCR fragments sized during CE? Can you describe what an internal lane standard and allelic ladder is?

Unknown PCR fragments are sized during based on the allelic ladder, which is an artificial mix of common alleles that are present in the human population for a particular STR marker (provides reference DNA size)

The internal lane standard is included in each DNA sample and it helps calibrate the peak data points to their DNA size

Why are there different colors for the STR alleles in the electropherogram?

There are different colors because they correspond with the different fluorescent dyes used.

You have provided a statistical analysis for the DNA match you obtained. Can you describe the method you used for statistical analysis?

For our statistical analysis we used a method called random match probability

RMP is the probability of selecting the observed profile from a population of random, unrelated individuals

RMP is calculated by using observed allele frequencies to calculate the genotype frequency for each locus and use the product rule to multiply them all together for the profile frequency

Why did you perform the calculation for all four populations designated in the database?

We performed the calculations for all four populations because we cannot assume someone’s ethnicity passed on someone’s self reporting

Also we were not given information about the race for the suspect

Do you know how many zeroes are in your numbers? Are these numbers greater than the population of the world?

Caucasian - 27 zeros

African American - 30 zeros

Hispanic - 30 zeros

Asian - 27 zeros

And all of these numbers are greater than the population