How long does it take for DNA to degrade beyond use in a crime?

TKHDebater

Senior member
Jan 2, 2003
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I'm in an Honors Natural Science class and we've been assigned a mock trial. The details are below. My question is, how long would the body had to have been sitting before DNA quality was reduced enough to not be 100% accurate in court. Thanks


At approximately 9:00 a.m. Pinellas Police found Bessie L. Watts, 75-years-old dead in her home. Neighbors had not seen her for several days and became suspicious so they called police. She was found lying on the floor of her bedroom, partially decomposed. There appeared to be signs of a struggle. Blood was found on Mrs. Watt?s nightgown and a few drops were also found on the floor by the body. An autopsy determined cause of death to be a single gunshot wound to her head. There were no signs of GSR on her hands or clothing, but there was a significant amount around the head wound. In addition there were no signs of forced entry to her home. No weapon was found.
Interviews with neighbors and friends resulted in a number of suspects who were investigated and questioned. Among those questioned was Samantha White a friend and long-time neighbor of Mrs. Watts. She and Bessie had an argument a few weeks back about a world famous cherry pie recipe. Neighbors heard the two women arguing about the recipe. Mrs. Watt?s had accused Ms. White of stealing her recipe and using it to win the pie contest at the state fair earlier in the year. Neighbors reported that Ms White denied any such doing. Ms. White denies any involvement in Mrs. Watt?s murder, but does admit to being in her home several times to visit. Ms. White has a few bruises on her face and what appears to be a cut on her right hand.
 

EyeMWing

Banned
Jun 13, 2003
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Well, considering DNA from 20 years ago is being used on a fairly routine basis to exonerate the convicted... A DAMN long time.
 

gopunk

Lifer
Jul 7, 2001
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Originally posted by: EyeMWing
Well, considering DNA from 20 years ago is being used on a fairly routine basis to exonerate the convicted... A DAMN long time.

often times that DNA has been preserved... so it wouldn't have been degrading for all of that 20 years
 

Spencer278

Diamond Member
Oct 11, 2002
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There is about a .0000001% chance that the sample would degrade and match a different person.
 

theNEOone

Diamond Member
Apr 22, 2001
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DNA can exist indefinitely under many conditions, it's actually a fairly robust molecule. it all depends on the conditions, but for your purposes i would imagine that DNA would not have degraded beyond the point of being unusable. the "story" is giving you some hints that DNA analysis is involved, so i wouldn't think it a stretch for you to check the crime scene for the suspects blood. also, the "cut" on ms. white might actually be a scratch. you could check uner the fingernails of the victim and look for trace amounts of blood or skin cells and run this sample for dna analysis.


=|
 

Spencer278

Diamond Member
Oct 11, 2002
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Go for a plea bargin. There is no beliviable reason why your client bleed in the murder victims house and then moments latter the person is shot in the head. How do you plan on answering the question why didn't you clean up your blood before you left.