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Comment by ggambetta | Hacker News Reader

Wearing my fiction writer hat - I found this fragment fascinating:

DNA analysis is now one of the key tools police use in forensic analysis and identification cases.

It didn't exist back in 1970.

But it turns out several tissue samples from the woman's organs, including from her lungs, heart, adrenal gland and ovaries, have been stored at Haukeland University Hospital.

Makes me wonder what kind of "perfect crime" may be committed today, where the criminal literally achieved technical perfection, only to be caught 40 years later by a forensic technique that doesn't even exist today.

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This happened to Lance Armstrong. As one investigator put it, his 1999 urine was meant to pass the drugs tests available in 1999. But when subjected to tests developed 5 years later, it failed.

https://en.wikipedia.org/wiki/Lance_Armstrong#Tour_de_France...

This is quite common these days, e.g. many atheletes lost their 2008 Olympic medals due to retesting in late 2016.

Encrypted records of the crime but which you refuse to decode. Your drive is imaged and stored and at some point in the future, the algorithm is revealed to have a flaw which leaks key information into some part of the cipher text.

Wasn't one of the things we learned from Snowden that the NSA archives huge amounts of encrypted data because they can't crack it right now, but might in the future, given enough technical advancements?

>Makes me wonder what kind of "perfect crime" may be committed today, where the criminal literally achieved technical perfection, only to be caught 40 years later by a forensic technique that doesn't even exist today.

This happens all the time, when DNA became a core forensic tool a lot of cold cases were solved, and a lot of people were also acquitted.

That said since no one knew about DNA samples were often not preserved also due to the cost of preservation in some cases evidence was destroyed that latter primarily affects acquittal efforts since after you've lost all your appeals the evidence can be destroyed legally to save costs. IIRC there was a proposal or even a change in law to mandate the preservation of evidence for all convictions on death row until they are executed but since in the US it's a state by state issue it's likely not to be uniform.

It's actually interesting to note that over time I've become increasingly skeptical of ferensics.

My wife works daily in a genetics and neuroscience lab. She said typically one out of three experiments they do, even under the best conditions don't turn out. Given how little forensic DNA is often collected, and how often DNA either becomes contaminated or the experiment/process fails, I often question the validity of tests.

My wife doubts the validity even more than I do lol

And you're right to. Without proof of blind sample testing and rigorous QA on the process, there's no reason to trust the results. And that type of evidence, if accepted, would only wisely be used for ruling out suspects.

Even considering the defense as the null hypothesis, the US legal process is not as scientific in some very important ways as it could be.

Well it's not necessarily applicable.

DNA sequencing in forensics isn't a full sequencing it's just a profile with an 1 in n match usually in the low millions which outside of direct same sex familial match is going to be highly unlikely to be a false positive.

Forensic evidence doesn't exists in a vacuum it's looked at in context.

It's also worthy to note that most cases aren't an episode of CSI and most convictions still rely on witness testimony and or confessions.

Thats not to say that there haven't been bad practices in he past ranging from bad science to individual malpractice and even malice. But it's still better than just having he said she said, as forensics allow you to verify testimonies and build a plausible depicture of events.

Has the false positive rate been empirically evaluated?

The fact that most convictions rely on witnesses doesn't make me any happier. Human memory is deeply flawed.

DNA analysis was used to reinvestigate the Lake Bodom muders (which happened in 1960): https://en.wikipedia.org/wiki/Lake_Bodom_murders

It's even used to investigate Jack the Ripper: https://en.wikipedia.org/wiki/Aaron_Kosminski#DNA_evidence

time travel

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