Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014...
-
Upload
kevin-underwood -
Category
Documents
-
view
218 -
download
0
Transcript of Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014...
![Page 1: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/1.jpg)
Getting Past First Bayeswith DNA Mixtures
American Academy of Forensic SciencesAmerican Academy of Forensic SciencesFebruary, 2014February, 2014
Seattle, WASeattle, WA
Mark W Perlin, PhD, MD, PhD Mark W Perlin, PhD, MD, PhD Cybergenetics, Pittsburgh, PACybergenetics, Pittsburgh, PA
Cybergenetics © 2003-2014Cybergenetics © 2003-2014
![Page 2: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/2.jpg)
Prior genotype probability
Pro
babi
lity
Allele pair
Genotype of contributor at locus: random variable
![Page 3: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/3.jpg)
DNA mixture data
peakheight
peak size
1
Use all the data
![Page 4: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/4.jpg)
Genotype likelihood
Major contributor allele pair
Minor Minor contributor contributor allele pairallele pair
Higher with good explanation
![Page 5: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/5.jpg)
Genotype likelihood
Major contributor allele pair
Minor Minor contributor contributor allele pairallele pair
Lower with poor explanation
![Page 6: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/6.jpg)
Genotype likelihood
2
Consider all genotype hypotheses
Allele pair
![Page 7: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/7.jpg)
Posterior probability
Update beliefs by combining prior belief with likelihood to get posterior belief
Divide by total to sum to 1
The Reverend Thomas Bayes
![Page 8: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/8.jpg)
Posterior genotype probability
3 Don't confuse likelihood with probability
![Page 9: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/9.jpg)
Posterior genotype probability
56%
1%3%
10%
23%
5%
Pro
babi
lity
Allele pair
![Page 10: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/10.jpg)
Match information
Dr. Alan TuringDecoded the WWII Enigma Machine
Likelihood ratio (LR)Bayes update for hypothesis and itsalternative
Measures how data changes our belief
![Page 11: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/11.jpg)
Genotype match information
4Use simple ratios, not complex formulas
![Page 12: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/12.jpg)
Genotype match information
Prob(evidence match)
Prob(coincidental match)ratio =10.38
56%
5.4%
Pro
babi
lity
Allele pair5 Make meaningful comparisons
![Page 13: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/13.jpg)
NIST teaches Bayes
April 2013, NIST WebcastDNA Analyst Training on
Mixture Interpretation
Google: nist trueallele corrections
http://www.cybgen.com/information/newsroom/2013/apr/Corrections-to-NIST-mixture-interpretation-webcast-misstatements-about-TrueAllele-Casework.shtml
![Page 14: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/14.jpg)
Bayes for beginners
1. Use all the data
2. Consider all genotype hypotheses
3. Don't confuse likelihood with probability
4. Use simple ratios, not complex formulas
5. Make meaningful comparisons
![Page 15: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/15.jpg)
Bringing probabilistic genotyping into the lab & courtroom
• Understand Bayesian update• Unlearn qualitative peak thresholds• Learn quantitative genotype modeling• Train to use the software & certification• Validate the genotyping system• Develop standard operating procedures
• Succeed in admissibility hearings• Write case reports on match results• Prepare necessary trial materials• Educate trial attorneys for court• Explain the LR to jurors and judges• Answer cross-examination questions
![Page 16: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/16.jpg)
Genotyping experience
Devise the math & algorithms 20 years
Develop computer systems 15 years
Support users and workflow 10 laboratories
Validate system reliability 20 studies
Educate the community 50 talks
Train & certify analysts 200 students
Go to court for admissibility 5 hearings
Testify about LR results 20 trials
Educate lawyers and laymen 1,000 people
Make the ideas understandable 150 reports
![Page 17: Getting Past First Bayes with DNA Mixtures American Academy of Forensic Sciences February, 2014 Seattle, WA Mark W Perlin, PhD, MD, PhD Cybergenetics,](https://reader035.fdocuments.us/reader035/viewer/2022062409/5697bf9a1a28abf838c924d4/html5/thumbnails/17.jpg)
Learning about genotyping
http://www.cybgen.com/information
• Courses• Newsletters• Newsroom• Presentations• Publications
http://www.youtube.com/user/TrueAlleleTrueAllele YouTube channel