Forensic DNA Lecture 10 Genetics & Society Honor 3215, Fall 2008 Bryan Benham Forensic DNA Forensics is the application of scientific methods and technology for legal purposes. Forensic genetic (DNA) is, thus, the application of genetic science for legal purposes. 2 What do you know about Forensic DNA? Cold Case Law & Order Missing 3 Forensic DNA: Applications 4 Still Guilty After All These Years New York Times, April 8, 2007 OP-ED CONTRIBUTOR By SCOTT TUROW THIS Friday a 33-year-old man named Juan Luna will go on trial here [Chicago] for the murder of seven people in a Brown’s Chicken restaurant in Palatine, Ill., on Jan. 8, 1993. The investigation of the murders, in which the victims’ bloody corpses were discovered in the restaurant freezer, languished for more than a decade until Mr. Luna’s DNA was identified in the saliva found on a chicken bone at the crime scene. http://www.nytimes.com/2007/04/08/opinion/08turow.html 5 Other Criminal Uses 4 •! “John/Jane Doe” DNA and Statutes of Limitation –! The statute of limitations in Wisconsin on a cold case of a serial rapist (three assaults) was soon to take effect. The criminal code held that if the name of the suspect was not known, a valid warrant could be brought on “any description” which identified that person with reasonable certainty. Norm Gahn, the assistant district attorney, made out the warrant for an unknown male with a specific DNA profile. This kept the case open, but still no success. (See p. 275 in DNA) 6Other Criminal Uses 1 •! Pet cat hair implicates murder suspect, 1997, Nature, 386: 774. –! Estranged husband of murdered woman suspected of murder because of snowy white cat hair found on jacket near crime scene matched the cat belonging to man’s parents. 7 Other Criminal Uses 2 •! Angiosperm Witness –! Murderer convicted on DNA evidence from plants. Pager found by young woman murdered in Phoenix led police to suspect, who admitted picking up the victim, but clamed she robed him. Forensic evidence from seed pods of palo verde trees found in suspect’s truck definitively linked truck/suspect to crime scene. –! Scientific American Frontiers, PBS TV 8 Innocence Project Founded in 1992 by Barry Scheck and Peter Neufeld to assist prisoners who could be proven innocent through DNA testing. To date 208 people in the United States have been exonerated by DNA testing, including 15 who served time on death row. The Innocence Project’s mission also aims to bring substantive reform to the judicial system. (More next time…) www.innocenceproject.org 9 Other Criminal Uses 3 •! DNA evidence identifies relative of suspect –! DNA evidence from a triple rape/murder in 1973 in South Wales was prepared but found no matches in National DNA Database. Rather than looking for match, forensic experts looked for near-matches, hoping to track down the suspect via relatives. Eventually led to Joe Kappen, then dead of cancer in 1991. Kappen’s body exhumed and profiled resulting in a match. (See p. 276 in DNA) 10 Family Ties: Jefferson & Hemings •!In a 1998 Nature study use of Y-chromosome to determine Descendant’s relationship to Sally Hemings’ sons, Madison and Easton. •!Descendants of Easton, but not Madison have link with Jeffersons. •!Conclusion: at least one of Sally Hemings’ sons is fathered by a Jefferson. 11 DNA Testing Reunites Families Separated by War (in El Salvador) News Hour, Feb. 15, 2007 Thousands of children kidnapped during a civil war in El Salvador in the 1980s, but new DNA procedures are helping reunite parents with their now grown children. http://www.pbs.org/newshour/bb/science/jan-june07/dna_02-15.html 12Other Forensic DNA Uses •! Identify dead in mass disasters and war –! 9/11, Katrina, Iraq and others •! DNA database for endangered species and animal populations –! Declining Grizzle populations, poached animals, Zurich Zoo Ibis Population •! Tomb of the Unknowns –! 1998 (Blassie), Czar Romanov, etc. •! Heritage and archeological finds –! Kennewick man, Columbus and Jefferson’s ancestors, Peruvian Ice Maiden •! Wine heritage –! Tracking pedigree •! Super Bowl and Olympic memorabilia –! Unique identifiers 13 Forensic DNA: Kinship & Identity 14 Accidental Discovery, 1985 •! (Sir) Alec Jeffreys •! Studies genetic variation and mutation in human and animal DNA (Ancestry) •! Discovered a way to uniquely identify individuals with “Junk DNA” •! “DNA Fingerprints” –! Hypervariable 'minisatellite' regions in human DNA. Jeffreys, A.J., Wilson, V. & Thein, S.L. Nature, 314, 67-73 (1985) http://www.sciencewatch.com/interviews/sir_alec_jeffreys.htm 15 In theory, we knew [DNA Fingerprinting] could be used for forensic identification and for paternity testing. It could also be used to establish whether twins were identical – important information in transplantation operations. It could be applied to bone marrow grafts to see if they’d taken or not. We could also see that the technique [would work] on animals and birds. We could figure out how creatures are related to one another – if you wanted to understand the natural history of a species, this is basic information. We could also see it being applied to conservation biology. The list of applications seemed endless. – Alec Jeffreys 16 “Junk” DNA and You •! Any two individuals (unrelated) are 99.9+% genetically identical (same order of genes) –! That means, ~3 billion base pairs in human genome, ~0.1% = ~3 million base pairs are different between individuals, and inherited from parents. •! Most base pair polymorphisms (changes in alleles) occur in non-coding areas of DNA; so called “junk” DNA. (Why?) –! Some areas of junk DNA contain more polymorphisms than other areas; these act as markers or loci for DNA Fingerprinting. (Why?) –! In these areas of junk DNA there are repeated sequences found next to each other, called tandem repeats. Short instances are Short Tandem Repeats, STR: … TCAT TCAT TCAT TCAT TCAT… •! When multiple loci are examined, the number of tandem repeats in these loci are unique across individuals, but are inherited from parents. 17 Comparing STR at Two Loci A B 5 repeats 6 repeats 5 repeats 3 repeats A B 5 repeats 4 repeats 4 repeats 5 repeats Person 1 Person 2 18Forensic DNACompareElectrophoresis*for profilePCRExtract DNAEvidence SampleElectrophroesis*for profilePCRExtract DNASuspect Sample19 From Watson,