DNA

Double helix Nucleotides (ACTG) Connected to a sugar molecule and phosphate group (AT and CG bonding) Watson and Crick are given credit for the double helix

Each individual’s DNA is unique (except for ID twins) Normally we all have 23 pairs Only id twins will be exactly the same

organic molecules that are the building blocks of nucleic acids, such as DNA and RNA.

12 required testing points

Blood Semen Saliva Urine (Usually epithelial cells, not the urine itself. Cells fall to the bottom) Hair Teeth Bone Tissue

Sir Alec Jefferies

Colin Pitchfork

Suspect DNA on victim’s body, clothing, belongings, etc. Victim DNA on suspect’s body, clothing, belongings, etc. Suspect or victim DNA on weapons, masks, cigarettes, drinking cups Hit and run victim DNA on automobile

Can tell us the contributor, but not the intent/ how or when it was deposited

• Extraction • Quantitation • PCR Amplification of Multiple STR markers

Short Tandem Repeats PCR based-amendable to small sample size Can perform multiple tests at one time Relatively short analysis time High power of discrimination Looks at 24 locations of DNA with it’s own statistical significance

Match= inclusion No match= exclusion

Person has two copies of the same gene, one from mom, one from dad Ex. 30

Ex. 13/14 Two different characteristics inherited from the parents

Discrimination- the potential power of a system to differentiate between any two people chose at random One forensically significant difference is an exclusion The more regions of DNA match, less likely another individual would match at all regions

The potential power of a system to differentiate between any two people chose at random

Mixed profiles that can be resolved Semen differential extraction to isolate sperm They use a different technology to separate the female cells from the sperm with heat, etc.

Every male on the paternal line shares the same Y-STR profile But beneficial when the DNA is mixed with female DNA Paternal line focused

maternal line DNA testing

Single nucleotide polymorphisms

Personnel meet competency and proficiency standards Techniques are validated and accepted 100% of casework is reviewed for technical More

Lab precautions - Clean environment, use gloves at all times - Separate areas of lab for different functions - Known and unknown samples extracted at different times so attorneys can’t ask about contamination Testing precautions - Reagent blank - Positive and negative control samples SAMPLE RETESTING

Combined DNA Index System FBI created a situation where state labs across states and exchange and compare DNA profiles electronically Became super beneficial with someone who was raping while in the military and he was in different states Started in 1989 when DNA profiling was relatively new - 2 major objectives - To assist police in identification of suspects in violent crimes - Increase effectiveness of forensic laboratories in DNA labs with frequency calibrations - Get from lecture at around 1.5 hours - Labs have to be local, state, or federal to get CODIS

casework