3 ms·

Maybe you know more about this than me, something that makes me uneasy about DNA evidence: Say you can confirm a sample is 100% a certain person. How do invest

by djleni 4y ago

Maybe you know more about this than me, something that makes me uneasy about DNA evidence: Say you can confirm a sample is 100% a certain person. How do investigators have any idea how it got there? How do you know it’s from a criminal and not the guy that stocked the convenience store shelves? I tried to look into this and maybe I was searching the wrong thing but found nothing.

boomboomsubban 4y ago
>How do investigators have any idea how it got there? They often can't be certain, and I'm sure somebody is in prison because they're DNA was in an inconvenient place, but it's a far superior form of evidence than the other methods mentioned. Unless a crime is widely watched in person with supporting recordings and DNA evidence, it's basically impossible to be a 100% certain of what happened. That's why court only attempts to prove guilt beyond reasonable doubt.
thaumasiotes 4y ago
The relevant concept is called "chain of custody"; essentially you're trusting every person who ever handled the sample to have correctly documented where they got it and what they did with it. This is the same way we guarantee the integrity of elections.
jessaustin 4y ago
One catchphrase is "means, motive, opportunity". DNA can indicate a possible opportunity, in that a suspect's DNA can be shown to have appeared in the same place a crime occurred. That doesn't address means or motive, i.e. whether the suspect had the ability or inclination to commit the crime. If I were on a jury and a DNA sample was all the prosecution had, my verdict would be not guilty. Keeping a massive DNA database and using it to convict someone, anyone because a crime occurred near something they touched before would be fallacious and unjust. However, if we already had other reasons to suspect someone, and DNA gives us another, that's much more powerful.

by djleni 4y ago

boomboomsubban 4y ago

>How do investigators have any idea how it got there? They often can't be certain, and I'm sure somebody is in prison because they're DNA was in an inconvenient place, but it's a far superior form of evidence than the other methods mentioned. Unless a crime is widely watched in person with supporting recordings and DNA evidence, it's basically impossible to be a 100% certain of what happened. That's why court only attempts to prove guilt beyond reasonable doubt.

thaumasiotes 4y ago

The relevant concept is called "chain of custody"; essentially you're trusting every person who ever handled the sample to have correctly documented where they got it and what they did with it. This is the same way we guarantee the integrity of elections.

jessaustin 4y ago

One catchphrase is "means, motive, opportunity". DNA can indicate a possible opportunity, in that a suspect's DNA can be shown to have appeared in the same place a crime occurred. That doesn't address means or motive, i.e. whether the suspect had the ability or inclination to commit the crime. If I were on a jury and a DNA sample was all the prosecution had, my verdict would be not guilty. Keeping a massive DNA database and using it to convict someone, anyone because a crime occurred near something they touched before would be fallacious and unjust. However, if we already had other reasons to suspect someone, and DNA gives us another, that's much more powerful.