How long
does it typically take for DNA results to come back in a murder case,
specifically blood on a knife? Could the agency get a preliminary report (i.e.
blood type) any faster?
Amryn says:
Each lab
will have its own turnaround time for DNA. For most state crime labs or local
agency labs (meaning those that are attached to a law enforcement agency) the
turnaround time is likely to be several weeks/months. This is because they may
receive dozens of cases per day, certainly per week, and cases are usually
worked in the order they are received. Some cases may only have one or two
samples that need DNA testing, while others may require 40 or 50 (this is not
as common, but not unheard of either.)
In some
cases, a district attorney or someone in charge of the lab may declare the case
a “rush” or an “expedite” (usually documented in the form of a letter), in
which case it jumps to the front of the line. A lab may drop everything else to
work on this case, depending on the scope of the case. Usually one analyst is
assigned a case, but may ask others for help to get the results out faster.
Best
scenario (which never happens), DNA could possibly be done on an exhibit as
small as a knife in 48 hours. Then the report has to be reviewed by two other
analysts before it can be sent to law enforcement. That’s not including a
search of the FBI database if there are no suspects in the case. A manual
search of the database may be done in rare cases, otherwise it’ll take another
week to see if the DNA profile “hits” anyone in the database.
Most places
don’t do blood typing anymore because it’s kind of time consuming and obviously
not as unique as a DNA profile. The most that could be said in a preliminary
report is to verify that the stain on the knife is, in fact, blood. It seems
silly, but they do have to verify that it is blood and not cocktail sauce or
something on the weapon.***********************************************************************
Amryn Cross is a full-time forensic scientist and author of romantic suspense novels. Her first novel, Learning to Die, will be released in September. In her spare time, she enjoys college football, reading, watching movies, and researching her next novel. You can connect with Amryn via her website, Twitter and Facebook.
I tried leaving a comment and it was lost when I hit submit. I'll try again. My question is about cold cases. Are you able to test for DNA from blood on a knife or clothes from 30-40 years old? Also, if the remains of a body were found in a mine shaft, could you tell the manner of death from that same time or even older, say, 150 years old? How would you do this and how long would it take? Thanks so much for your help! ::)
ReplyDeleteHi Rebecca,
DeleteThanks so much for leaving your question. I'll get this to Amryn for you for an expert answer.