1. DNA technology in court
Dan E. Krane, Wright State University, Dayton, OH
Forensic DNA Profiling Video Series
Forensic Bioinformatics (

2. DNA technology in court
Criminal Prosecution
Unprecedented sensitivity and specificity for typing biological samples
Growing use of databanks and dragnets to identify suspects
Rapidly becoming cheaper and faster

3. Possible DNA sources
Slide illustrating that with STR’s we can do “non-conventional” evidence such as dandruff and skin cells from the handle of a knife.

4. DNA technology in court
Criminal Defense
Unprecedented sensitivity and specificity for typing biological samples
Potential support for alternative theories of the case
Generation of alternative suspects
In a July, 2003 interview with investigators, Kobe Bryant stated that he had had consensual sex with a 19-year-old hotel employee. He is shown here with his attorney Pamela Mackey.

5. DNA technology in court
Post-conviction exonerations (300 as of September, 2012) based on DNA evidence have revealed problems with the justice system
Damon Thibodeaux had been on death row in Louisiana since October 1997 until he was exonerated of the murder and rape of his 14-year old step-cousin. He was the 300th to be exonerated by DNA evidence and the 18th to have served time on death row. The 300 DNA exonerees served a combined total of 4,013 years in prison for crimes that they did not commit. In almost half of the cases the true perpetrator was caught. But, had the true perpetrator been correctly captured in the first place more than 130 violent crimes could have been prevented. The Innocence Project only takes on cases if three criteria are met: 1) the convicted individual has maintained their innocence throughout, 2) DNA test results would be able to prove innocence, and 3) material is available for DNA testing.

6. Factors associated with wrongful convictions
Saks & Koehler, Science (2005)
The Coming Paradigm Shift in Forensic Identification Science, Science, 5 August, 2005, 309: Based on case analysis of 86 DNA exonerations. Red bars indicate factors related to forensic science. Percentages exceed 100% because more than one factor was found in many cases.

7. What is a good source of DNA?
Blood, saliva, semen, tissues, pretty much anything that comes in contact with a person.

8. DNA content of biological samples
Trillions of cells

9. DNA content of biological samples
Trillions of cells
Roughly 100 cells

10. DNA content of biological samples
Trillions of cells
Roughly 100 cells
Each cell contains 6 to 7 pg of DNA
DNA profiling kits generally recommend using between 500 and 1,000 pg of template DNA

11. DNA content of biological samples
Trillions of cells
Roughly 100 cells
Each cell contains 6 to 7 pg of DNA
DNA profiling kits generally recommend using between 500 and 1,000 pg of template DNA
That works out to roughly 100 to 200 cells

12. What is a picogram? 1 gram = 1/4th of a packet of sugar
1 milligram = a single crystal of sugar
1 nanogram = one 1000th of a crystal of sugar
1 picogram = one billionth of a gram

13. What is a good source of DNA?
Blood, saliva, semen, tissues, pretty much anything that comes in contact with a person.
But, the presence of a DNA profile says nothing about the time frame or circumstances of its transfer.

14. How is DNA analyzed? Isolation and purification PCR amplification
Size fractionation
Computer processing
Statistical weighting

15. DNA technology in court
Used in prosecutions, defenses, and post-conviction

16. DNA technology in court
Used in prosecutions, defenses, and post-conviction
DNA tests are very sensitive

17. DNA technology in court
Used in prosecutions, defenses, and post-conviction
DNA tests are very sensitive
Test results need to be interpreted carefully

18. DNA technology in court
Dan E. Krane, Wright State University, Dayton, OH
Forensic DNA Profiling Video Series
Forensic Bioinformatics (