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Slide 2 Extraction: Why do I know that word? Slide 3 Inside the Crime Lab: What happens next? Slide 4 How do they get the DNA off the shoes? Real answer: -They extract it. Slide 5 Slide 6 Lets talk about how this is SUPPOSED to be done: Photo courtesy of Dr. Mitch Holland Slide 7 Picture courtesy of Dr. Mitch Holland Slide 8 The scientist is then to return the sample, remove the paper, clean the worksite, change their gloves before moving on to the next sample What happens if you dont?? Slide 9 Questioneds before Knowns Slide 10 Exceptions Slide 11 Rule Slide 12 Can you look into the future and tell me why this is a good idea? Slide 13 Practical Application Slide 14 Practical application further: If the questioned sample is contaminated with the defendants known sample at the lab, every time you test the questioned sample, it will show the defendants profile even if he was in Topeka at the time of the crime. Slide 15 Finally, when they want your clients sample and they will... The American Bar Association recently released the ABA Criminal Justice Standards on DNA Evidence. Slide 16 2.2 (b)(i)(C) (i) If the person from whom the sample is to be collected is suspected of committing a crime, an order should issue only upon an application demonstrating: (A) probable cause that a serious crime has been committed, and (B) if the sample is to be collected from a person is: (1) a sample collected by a physically noninvasive means, reasonable suspicion that the person committed the crime charged; and (2) a sample collected by physically invasive means, probable cause that the person committed the crime charged; and (C)that the sample will assist in determining whether the person committed the crime. Slide 17 Controls! The idea is that if there is a contamination, it will show up in the control. Using the previous example, if the defendants profile contaminates the questioned, it ideally will also contaminate the control. Slide 18 Controls: Positive Controls Negative Controls reagent blanks Negative amplification control Blind Controls/QC sample. Slide 19 Processing controls The controls are treated just as if they were case samples. Slide 20 Positive Control The Positive Control has a known, correct answer. It comes with the kit and is the same every time. Slide 21 Negative control Slide 22 Slide 23 Blind Control The Blind Control also has a right answer. However, this right answer is not immediately known. It is the DNA profile of one of the scientists in the lab. When they do DNA testing, they check out a DNA profile from the lab supervisor, who keeps track of whos sample was given. The scientist must compare the answer known to the supervisor with the answer they got during testing to confirm the test was done correctly. Failure to match SHOULD result in a retest. Slide 24 Controls generally The idea behind controls, of course, is to have a way to see if you contaminated your sample. Controls arent the exclusive or only way to tell, however. Slide 25 Other ways to detect contamination Known samples, such as from a victim or a suspect, should generally contain no more than two alleles (remember that word?) at each locus. Slide 26 A few words about alleles in single source samples: Heterozygote In the first blue locus, the individual has a 16 and a 17 (one from mom and one from dad, remember?). Homozygote At the next locus, we only see a 15. Freak of nature?? No!! This person got a 15 from mom AND a 15 from dad. Slide 27 How do you extract it? Slide 28 Dawn takes grease out of your way... HOW? Slide 29 Extraction in pictures a photo essay Put the cells in the test tube... Slide 30 Slide 31 Extraction photo essay continued Break open the walls of the cell, using detergent and salt. Slide 32 For cell walls Slide 33 Final steps... More chemicals are added to break open the yolk or nucleus. Slide 34 For the nucleus walls Slide 35 Recall the yolks represent the nucleus of the cell. Slide 36 Slide 37 Slide 38