Our current lab procedure requires that the evidence that is being requested for latent prints, DNA, and firearms be processed for latent prints first. Firearms is always last because the FA examiners don't wear gloves during their test fires. There have been occasions when the DNA from examiners in both latent print and firearms units have been identified on items of evidence. But, this happens very infrequently.
Recently, the DNA Unit has suggested that we change gloves between each item of evidence. Or, as an alternative to that precaution have the latent print examiners swab the items prior to latent print processing.
So, I have the following questions:
1. If your lab performs latent print processing, what precautions does your lab utilize in order to prevent contamination?
2. What is your policy/practice on processing sequence (do you swab then LP process or vice-versa or a combination of both depending on the surfaces, etc)?
3. Will your DNA Unit process an item after it's been processed for LPs?
The ol' chicken and the egg question (DNA & Latent print
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Kelly Speckels
- Posts: 3
- Joined: Tue Sep 11, 2007 4:05 pm
- Location: Mesa, AZ
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sharon cook
- Posts: 192
- Joined: Thu Dec 08, 2005 2:27 pm
- Location: Austin, Texas
I have worked for state, county, and city crime labs and DNA is ALWAYS worked first. Then LP processing, then firearms. The DNA people naturally wear gloves when they swab. Sometimes firearms is worked first, but rarely, because they don't wear gloves, and even if they do wear gloves, the mere handling of the firearms can smudge any latent prints.
It is possible to develop a DNA profile after LP processing...studies have been done to show that most LP processing does not interfere with DNA, but it's best to do DNA first because it is so sensitive.
It is possible to develop a DNA profile after LP processing...studies have been done to show that most LP processing does not interfere with DNA, but it's best to do DNA first because it is so sensitive.
Take responsibility for your own actions
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Michele
- Posts: 384
- Joined: Tue Dec 06, 2005 10:40 am
Kelly,
A few years ago we started coordinating our efforts with our DNA lab and here’s what we decided.
We only use precautions when it’s stated that the evidence also needs to be tested for DNA.
When this happens, we do a light source inspection and CA, then photograph any results. We also use the precautions of changing gloves after we touch any item, we wear face masks, and use clean paper on all surfaces. Dye stains don’t destroy DNA but they do wash it off the object. Powders and brushes (even new ones) are seldom DNA free.
After we do this then we have the items sent to DNA with the information that it’s been CA’d (they need to know that DNA may be trapped under the CA and they may need to swab the item a little harder).
Then after DNA, the detectives can send the items back to us for additions processes (dye stains and powder).
I’m sure people will have issues with the way we do it but this works well for us.
Kerrie Cathcart swabbed the items herself when she worked for Alaska (now she’s in West Virginia) and had great success (but I don’t remember the numbers). We’ve thought about trying this ourselves but we’ve never got around to trying it.
A few years ago we started coordinating our efforts with our DNA lab and here’s what we decided.
We only use precautions when it’s stated that the evidence also needs to be tested for DNA.
When this happens, we do a light source inspection and CA, then photograph any results. We also use the precautions of changing gloves after we touch any item, we wear face masks, and use clean paper on all surfaces. Dye stains don’t destroy DNA but they do wash it off the object. Powders and brushes (even new ones) are seldom DNA free.
After we do this then we have the items sent to DNA with the information that it’s been CA’d (they need to know that DNA may be trapped under the CA and they may need to swab the item a little harder).
Then after DNA, the detectives can send the items back to us for additions processes (dye stains and powder).
I’m sure people will have issues with the way we do it but this works well for us.
Kerrie Cathcart swabbed the items herself when she worked for Alaska (now she’s in West Virginia) and had great success (but I don’t remember the numbers). We’ve thought about trying this ourselves but we’ve never got around to trying it.
Michele
The best way to escape from a problem is to solve it. Alan Saporta
There is nothing so useless as doing efficiently that which should not be done at all. Peter Drucker
(Applies to a full A prior to C and blind verification)
The best way to escape from a problem is to solve it. Alan Saporta
There is nothing so useless as doing efficiently that which should not be done at all. Peter Drucker
(Applies to a full A prior to C and blind verification)
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LittleE
- Posts: 2
- Joined: Thu Nov 29, 2007 1:23 pm
- Location: Phoenix
Kelly,
Here in Phoenix, the section that processes items for latents, also, in most cases swabs for possible biological material as well. It has been a year since I was in that section, but at the time I was there pretty much all guns were swabbed prior to latent print processing automatically. The swabbing was done in a sterile room following certain procedures, such was wipping down all surfaces with a 10% bleach solution, using clean butcher paper after the surface was bleached, switching out gloves often and always in between items.
Smooth surfaces were reserved for latents, while areas such as the grip of the gun which is usually raised would be swabbed. A visual examination was conducted during the process and if there was area that maybe blood, a small swab was collected of that as well--with the location and stain being documented photographically, as well as verbally.
Other items in which both processes (DNA and Latents) were requested were evaluated on a case by case basis-sometimes the Detective/Case agent had to choose between DNA or Latents, other times the item permitted areas to be swabbed and other areas to be processed for latents--th swab collection was commonly done by the Latent Print Processors in that situation--again using a sterile procedure.
At the time, DNA would not process for DNA if an item had already been processed for latents.
Again, since I am no longer in that area the procedures may have changed. Hope it helps.
--Emily
Here in Phoenix, the section that processes items for latents, also, in most cases swabs for possible biological material as well. It has been a year since I was in that section, but at the time I was there pretty much all guns were swabbed prior to latent print processing automatically. The swabbing was done in a sterile room following certain procedures, such was wipping down all surfaces with a 10% bleach solution, using clean butcher paper after the surface was bleached, switching out gloves often and always in between items.
Smooth surfaces were reserved for latents, while areas such as the grip of the gun which is usually raised would be swabbed. A visual examination was conducted during the process and if there was area that maybe blood, a small swab was collected of that as well--with the location and stain being documented photographically, as well as verbally.
Other items in which both processes (DNA and Latents) were requested were evaluated on a case by case basis-sometimes the Detective/Case agent had to choose between DNA or Latents, other times the item permitted areas to be swabbed and other areas to be processed for latents--th swab collection was commonly done by the Latent Print Processors in that situation--again using a sterile procedure.
At the time, DNA would not process for DNA if an item had already been processed for latents.
Again, since I am no longer in that area the procedures may have changed. Hope it helps.
--Emily
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Kathy Saviers
- Posts: 48
- Joined: Thu Jul 28, 2005 11:41 am
- Location: Salem, Oregon
No contact DNA
Kelly,
It appears that you and others are doing contact or touch DNA. In other words, swabbing for DNA to see if the suspect touched the item. In a class I took, it was demonstrated that DNA can transfer from one surface to another by a person's hand. The example given used a coffee mug that was washed clean. Someone touched the boss's coffee mug which wasn't cleaned and then, touched the clean one. The clean one was swabbed and the boss's DNA (along with the person touching the mug) showed up even though he never touched it. The prosecutor won't touch a case like this (pun intended). This is the reason why our State Lab doesn't waste their time on "contact" DNA.
But, to continue - if I have a beer can or bottle that needs to be checked for both DNA (saliva) and prints, I will swab the mouth area of a beer can or bottle first, then process for latent prints. If I get latent prints and get a match to a suspect, either by suggested name or via AFIS, the DNA will probably never be sent to the lab, sparing their time and costs. Plus, I can do the print work, including the AFIS work, within a day or two, whereas the wait on the results on a DNA request on a property crime can take as long as three years. On a person crime, it will be shorter but it will still be months.
Kathy
It appears that you and others are doing contact or touch DNA. In other words, swabbing for DNA to see if the suspect touched the item. In a class I took, it was demonstrated that DNA can transfer from one surface to another by a person's hand. The example given used a coffee mug that was washed clean. Someone touched the boss's coffee mug which wasn't cleaned and then, touched the clean one. The clean one was swabbed and the boss's DNA (along with the person touching the mug) showed up even though he never touched it. The prosecutor won't touch a case like this (pun intended). This is the reason why our State Lab doesn't waste their time on "contact" DNA.
But, to continue - if I have a beer can or bottle that needs to be checked for both DNA (saliva) and prints, I will swab the mouth area of a beer can or bottle first, then process for latent prints. If I get latent prints and get a match to a suspect, either by suggested name or via AFIS, the DNA will probably never be sent to the lab, sparing their time and costs. Plus, I can do the print work, including the AFIS work, within a day or two, whereas the wait on the results on a DNA request on a property crime can take as long as three years. On a person crime, it will be shorter but it will still be months.
Kathy