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I do hope the prosecutor is being careful about representing the strength of DNA evidence as this person was found through a fishing expedition via a DNA databa

I do hope the prosecutor is being careful about representing the strength of DNA evidence as this person was found through a fishing expedition via a DNA database. https://en.wikipedia.org/wiki/Prosecutor%27s_fallacy https://en.wikipedia.org/wiki/Prosecutor%27s_fallacy However, if the DNA evidence is the sole evidence against the accused and the accused was picked out of a large database of DNA profiles, the odds of the match being made at random may be increased, and less damaging to the defendant. The odds in this scenario do not relate to the odds of being guilty, they relate to the odds of being picked at random.

fixermark 8y ago
RTA. The relative match was used to narrow the suspect list and focus the investigation. I don't know the prosecutor is even going to bring up the ancestry DNA in the trial, and I doubt they will given the much more accurate direct DNA match they were able to acquire after staking out the suspect's home.
- clarkevans 8y ago
  Your reply, "I don't know the prosecutor is even going to bring up the ancestry DNA in the trial", exactly reflects my concern. Are you asserting that the DNA search and the "much more accurate DNA match" are statistically independent or that their dependence (overlapping genetic markers) is not relevant? P.S. Regarding your "RTA" ... from the Hacker News guidelines at the bottom of the page, I quote: "Please don't insinuate that someone hasn't read an article."
  - fixermark 8y ago
    Quite correct on the guidelines; my error. I don't know about the statistical independence of the DNA search and the match on separately-collected DNA directly from the suspect (once a suspect was found via the DNA search), but I think it's a little irrelevant; as long as existing laws aren't broken, I understand the court to generally not care how police became aware of evidence of a crime. Consider the oft-maligned "Stopped for a broken tail-light but there were drugs in the car" scenario. If the defendant goes to trial for the drug possession, the broken tail-light doesn't enter into the trial as evidence (mention of it may enter if someone asks the arresting officer why they chose to stop the defendant). Bringing the analogy around to this case: if a DNA relative match narrowed the field of suspects to the relatives of match candidate X, then the police still need evidence tying relative Y directly to the crime. In this case, they subsequently investigated Y and found such evidence. Should the initial scan of a DNA database for candidate X have been illegal? I think that's an open question. I personally don't think it should be.

fixermark 8y ago

RTA. The relative match was used to narrow the suspect list and focus the investigation. I don't know the prosecutor is even going to bring up the ancestry DNA in the trial, and I doubt they will given the much more accurate direct DNA match they were able to acquire after staking out the suspect's home.

clarkevans 8y ago
Your reply, "I don't know the prosecutor is even going to bring up the ancestry DNA in the trial", exactly reflects my concern. Are you asserting that the DNA search and the "much more accurate DNA match" are statistically independent or that their dependence (overlapping genetic markers) is not relevant? P.S. Regarding your "RTA" ... from the Hacker News guidelines at the bottom of the page, I quote: "Please don't insinuate that someone hasn't read an article."
- fixermark 8y ago
  Quite correct on the guidelines; my error. I don't know about the statistical independence of the DNA search and the match on separately-collected DNA directly from the suspect (once a suspect was found via the DNA search), but I think it's a little irrelevant; as long as existing laws aren't broken, I understand the court to generally not care how police became aware of evidence of a crime. Consider the oft-maligned "Stopped for a broken tail-light but there were drugs in the car" scenario. If the defendant goes to trial for the drug possession, the broken tail-light doesn't enter into the trial as evidence (mention of it may enter if someone asks the arresting officer why they chose to stop the defendant). Bringing the analogy around to this case: if a DNA relative match narrowed the field of suspects to the relatives of match candidate X, then the police still need evidence tying relative Y directly to the crime. In this case, they subsequently investigated Y and found such evidence. Should the initial scan of a DNA database for candidate X have been illegal? I think that's an open question. I personally don't think it should be.