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C-dub wrote:Also welcome. My knowledge of the collection of DNA is limited and my knowledge of the handling and testing is old. I did a little back in the middle 90's and almost took a job at a DNA lab in the late 90's, but I got a better offer from a different kind of lab, which took my career in a slightly different direction.

Unfortunately, I have almost no knowledge of the lab aspect of it at all. I made the assumption that my technique/collection habits were appropriate as I would see DNA reports come back in my cases with good data and had very little come back with disparities or inconsistencies that would point to error on my part. All I know is that DNA is the future. I could be wrong, but give it 10-15 years and it will surpass fingerprint comparison and collection. I don't think fingerprint work will ever go away, but advances are already here.

But to get it back on track, it would really depend on if the "suspect" in this case ever touched anything of the "victim" that has probative value. Meaning, I can find fingerprints in a house all day but if the victim tells me "Well, I let (suspect) in my home a few days ago and he lived here for a week, but now he's out and burglarized my home" what do his fingerprints prove? What value does it bring? I had this situation more times than I can count. I cannot prove, in a court of law, the time of fingerprints (or DNA for that matter). Could they have been left there during an authorized stay? Of course. Then your prosecution is out the window. That doesn't strictly pertain to this case, but it illustrates another aspect of issues that can arise. Even if the gun was touched in this Zimmerman case, what does it prove, inconclusively? His DNA could have gotten on the gun any number of ways. However, my knowledge of this case is strictly media biased so, please, if there is some aspect of this I am missing I want to know. To me, DNA evidence just seems like one of the least important aspects of this case.

Skiprr wrote:Welcome, sfemti33. And thanks for contributing your expertise.

Good to be here. I lurk daily but thought I should try and be more active on the board.

C-dub wrote:

baldeagle wrote:Note to Benjamin Crump. People don't shed DNA like feathers in a fight.

What makes you think we don't? We are shedding skin cells all the time and you're also going to leave some skin cells on just about anything you touch.

The problem with this is that it is true, yet may not yield results. (for reference, I was a forensic investigator for a police department). True, we may not shed DNA like feathers in a fight but "touch DNA" has been something used widely in recent years because we always leave something behind. Simple science is in "Locard's Principle", which essentially says you will always leave something and take something from a crime scene (but that doesn't mean the police with always FIND it). In the state I was in, touch DNA would ONLY be analyzed if it was a felony due to time and financial constraints. The great thing was, you could "dust" for fingerprints (and even "lift" them) and THEN swab for touch DNA and perhaps yield a result.

Most problems lie in evidence handling, knowledge base of the first individual who handle said evidence, and willingness/financial burden of those doing the test. If you do not handle/package the evidence correctly you can destroy or dilute the DNA (brush it off, like swiping away fingerprints). Transporting it, how you transport it, if you take the DNA swabs on scene and how you handle that, etc all can lead to destruction of any evidence. Unfortunately, I met many officers who were not well versed in evidence preservation and mishandled/destroyed evidence. Another factor is money and resources. The state lab could only test to a certain limit. For example, they may only be able to test to a level of 135 (to make it easy, let's say if there were 135 pieces of DNA on a penny they could find anything above that. But let's say, only 60 pieces of DNA were there, their test would not be sensitive enough even though there was DNA there). However, a private lab may be able to test as low as 35 pieces (because financial constraints are usually less in the private sector and they had better equipment), for a price, usually $15,000 or more, so we used that sparingly for budgetary reasons.

All I can say is that there are several methods, and even newer/better methods now, to obtain evidence but a lot of that depends on factors may be out of the control of the test. If DNA is there, then someone else handles the same place, you risk contamination and damage. If police personnel mishandle evidence, you risk contamination and damage. Even the simple act of transporting evidence in some sort container can, and does, obliterate all kinds of evidence.

Sorry to get all preachy, but what you see on CSI does not work in the real world. There are so many factors that pertain to this type of problem. (Also, if this was already mentioned I apologize. Didn't read all 1600+ posts).