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
As others have commented the government labs are underfunded and not the newest technology. The people certified to handle DNA evidence are also limited. The protocols required to ensure a sample is not contaminated are insanely strict, just breathing near the sample could contaminate it.
So taking into consideration the insane handing procedures you also have to clean between each sample and step. Processing a sample isn’t like in CSI where they just chop off the qtip into a vial, vortex it and shove it in a machine. There’s several steps that are used to clean and prepare and purify the DNA. There’s a bunch of stuff in your blood or cells that isn’t DNA, and all of that needs to be cleared away so the DNA sequencing can occur.
Then it’s possible that labs use next generation sequencing, which you can run just the full DNA as it is. But more likely they need to do a PCR step to replicate and amplify a certain portion of a DNA strand for comparison. Next gen is over 500$ a sample and takes half a day to run on a half a million dollar machine. PCR and regular sequencing would be 2-3 days of processing on machines that are 20-100k and only maybe 20$ a sample.
Every sample needs to be rerun to verify with a handful of standards and checks to verify the results. Once you run on the machine it spits out a bunch of meta data that then also needs to be processed. I’m not sure how they do it with human DNA sequences but I’ve had to do bioinformatics on environmental microbial samples. That step alone can take hours to days to analyse.
So in summary, cost, technology, limited resources and sheer volume of samples.
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