Transcript DNA: What, Where, When and Why From a Scientific Point of View

What is Mitochondrial DNA
(mtDNA)?
• Maternally inherited
– Every individual in the same maternal lineage should have
the same mtDNA sequence
• More sensitive than nuclear DNA
– Each cell contains 1000’s of copies of mtDNA vs. 1 copy
of nuclear DNA
• mtDNA is analyzed by sequencing
– Hypervariable I (HV1) and Hypervariable II (HV2) regions
- look for actual A,G,T,C sequence
When to use mtDNA testing
 Hair samples
with no or insufficient roots
 Cases where nuclear DNA analysis does not
result in sufficient information for a
conclusion
 Identity situations where there the only
reference available is a maternal relative
 **mtDNA is not good in cases of mixtures
mtDNA Report
Why would a Public Defender pursue
DNA testing?
• Results don’t have to be incriminating They
can also corroborate a story
• Questions about “no results” from evidence
that you think should yield a result
• Questions about mixtures
When to seek a DNA test vs. DNA
review
Listen to your client
• Re-test
– Results of first test
inconsistent with what
is expected
• No results were
obtained
– Mixture
• Lab can’t include or
exclude your client
• Review
– No results (no chart)
listed in report-only
conclusions
– Mixture- Is your client
really included?
– If you are confused by
the results
What to ask for Re: Discovery
At a Minimum
• Copy of complete case file (Including all raw
data)
– Serology
– DNA
• Copy of Protocols
– Standard Operating Procedures (SOP)
– Quality Assurance/Quality Control (QA/QC)
• Database information (Frequency tables)
What to ask for Re: Discovery
Additional Items
• Quality control records
– Kits used
– Critical Reagents
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Records of Proficiency Tests (each analyst)
Copies of Audit documents
Validation Information
Accreditation Information
What to look for in an expert
• Aspects to consider when picking an
expert and/or laboratory
– Price
– Turn-around time
– Accredited laboratory
– Experts who provide service both Defense
and those other guys (more credibility)
Thank You
Meghan E. Clement
LabCorp Forensic Identity Department
[email protected]