CDZ Using DNA to solve crime

[candycorn]

It would seem to me that if I were going to commit a crime, I would carry DNA from others with me and contaminate the crime scene then (if apprehended) hire a lab to do a DNA test.

??

You would carry around others DNA? What, would you spit it out after you had done your dastardly deed?

Well, no. Like if you were over at my condo and we were drinking some wine or whatever. If I wanted to implicate you in a crime that I was going to commit, I would carefully take the glass and put it into a ziploc bag for example being careful not to put my own prints on it. Then, when I did want to commit the crime, take the bag with the glass with me and place it at the crime scene. Or, if I'm visiting your house, I go into your restroom and pluck some hairs off of your hairbrush or get some out of the tub or whatever and put them into an envelope I have in my pocket or purse. Then when the crime takes place, I put your hair at the scene. Or, lets say I'm really anti-social and I see a guy at a convenience store throw away his can of Sprite or Budweiser into the garbage can. I fish it out and place it at the crime scene. If the cops come and question me, I say, well, I know Darkwind and the victim had some arguments in the past or say that I saw you leaving the scene... The reliance on DNA seems to create a rush to judgment that may not be there without the DNA. On one hand, it's proof positive that you have a connection to the victim or crime scene. On the other, it doesn't speak to what that link was. Your hair being there doesn't mean that you were there in other words.

Sure. And If I wanted to plant a glass with your fingerprints on it I could do something similar.

No system is going to be full proof.

True.

I was just pointing out how very convincing evidence could be planted as easily as you leaving it behind yourself.

Which is why we have juries. A single piece of DNA evidence would be only one piece in the entire evidence chain. Anything that corroborates that the accused was elsewhere when the offense took place would have just as much weight.

Mostly, DNA, like fingerprints, and other circumstantial evidence is used to contradict the sworn testimony of the accused. For example, a gun is found in the car of the accused. The accused states, "I never laid eyes on that gun before". The gun is tested for fingerprints and DNA and if his are found on the gun, he loses credibility. If enough credibility is lost, he will be convicted.

If the accused stated, "Yes, that's my gun. But, I never used it in the commission of a crime", then the DNA evidence does no damage to his credibility.

DNA has an out-sized place of importance with juries. Like if I corroborate that didn't know Karen Smith; the victim of a murder --like you said you didn't but your DNA was found at location on her bed sheets...I think the jury is probably correct to put more importance on the DNA than my testimony.