I’m watching Dateline and this suspect left a police interview and committed another murder. The first cops couldn’t arrest him because their evidence was all circumstantial. While they are looking for him now, the voiceover says DNA results are still not back. At this point it’s been several weeks. So Eli5 – DNA results: wtf takes so long?
Is there only one machine in the world? Can’t they move murder cases to the front of the line? Does the DNA fairy only come once a month? Does DNA take 500 hours to marinate? Can the cops buy another DNA machine? Do we need a GoFundMe?
In: 6
Ok, forensic DNA analyst here and so far none of these answers are correct. The answer is batching.
We could conceivably process 1 small case in 24 hours. So beginning to end, you can have your results tested, written and reviewed and back tomorrow.
But we have 100s of cases. A few come in every day. So we can have this awesome turnaround time for a few cases and also have this horrendous backlog or:
We can do 100s samples at a time over and over again, pushing them through the process together. So we can get you dozens of cases done in a few weeks, but none in 24 hours, and also no backlog.
It’s about batching. If you batch samples together they overall get done faster. If you have a serial rapist, or a missing child, of course, let’s push those through today on their own and get them done, but understand that when you prioritize cases like this, you’re pushing back other rapes and murders from being tested so push cases ahead thoughtfully.
Edit: Adding that murders don’t generally get pushed up the list because most times, someone already knows who did it and why. Most murders aren’t random. Rapes are random, though not always. Kidnappings can be random. Murder, rarely.
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