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Discussion Starter · #1 ·
I know cobis is dead but I'm just curious as to what the troopers needed the casing for? I'm not sure how they would get anything off the casing other than the extractor mark and possibly the way the firing pin hit? It just didn't make much sense to me.
 

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is was to link pistols to casings found at crime scenes. Needless to say it didnt solve any crimes that I am aware of.
 

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I know cobis is dead but I'm just curious as to what the troopers needed the casing for? I'm not sure how they would get anything off the casing other than the extractor mark and possibly the way the firing pin hit? It just didn't make much sense to me.
Doesn't make sense? New York Law.
 

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I know cobis is dead but I'm just curious as to what the troopers needed the casing for? I'm not sure how they would get anything off the casing other than the extractor mark and possibly the way the firing pin hit? It just didn't make much sense to me.
Actually, it's not so much the mark the firing pin or extractor makes, but what is called 'breech face impression'. The same force that propelled the bullet forward is applied to the remaining shell, but backwards. The shell slams into the breech face and the microscopic toolmarks are imprinted into the shell. This impression is said to be a unique identifier to the firearm. Breech face impression evidence is good, not great. It's not as good as matching the striation marks on a bullet. It can be useful for excluding a suspect firearm if the breech face impression is widely different from a shell casing at a crime scene. I think I read that the breech face impressions a firearm makes can change over time to some degree, so its not perfect. But think about this, if you have a crime scene with shell casings, you have a good chance of finding a bullet to match to a suspect weapon, so why bother with the shells in the first place?

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OIG Audit Report 05-30

I interned with the NYS crime lab in albany and saw the operation. It was a mess. The biggest problem is that cobis is redundant - I believe the FBI saves a shell casing too. If the evidence was so critical, send it to the feds. If the shell casing is databased by NY, it is surely databased by the FBI. The program costs something like $1.2 million a year, which is unbelievable to pay for 1 examiner and a computer. They were severely backlogged and it's a really labor intensive to make a match. I think I read that the cobis made 2 matches in its tenure, none which resulted in a conviction. It's a better idea to microstamp the firing pin (just kidding).
 

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Actually, it's not so much the mark the firing pin or extractor makes, but what is called 'breech face impression'. The same force that propelled the bullet forward is applied to the remaining shell, but backwards. The shell slams into the breech face and the microscopic toolmarks are imprinted into the shell. This impression is said to be a unique identifier to the firearm. Breech face impression evidence is good, not great. It's not as good as matching the striation marks on a bullet. It can be useful for excluding a suspect firearm if the breech face impression is widely different from a shell casing at a crime scene. I think I read that the breech face impressions a firearm makes can change over time to some degree, so its not perfect. But think about this, if you have a crime scene with shell casings, you have a good chance of finding a bullet to match to a suspect weapon, so why bother with the shells in the first place?

View attachment 8309

OIG Audit Report 05-30

I interned with the NYS crime lab in albany and saw the operation. It was a mess. The biggest problem is that cobis is redundant - I believe the FBI saves a shell casing too. If the evidence was so critical, send it to the feds. If the shell casing is databased by NY, it is surely databased by the FBI. The program costs something like $1.2 million a year, which is unbelievable to pay for 1 examiner and a computer. They were severely backlogged and it's a really labor intensive to make a match. I think I read that the cobis made 2 matches in its tenure, none which resulted in a conviction. It's a better idea to microstamp the firing pin (just kidding).
...call me an idiot...but lets see here...I rack the slide back on my Glock or Walther or any semi auto, I see the bolt face. I also see a rusty nail sitting next to it. I pick it up and scratch the bolt face. I have vastly changed it. I am off scott free? Not to mention what I have mentioned before, with respect to the "picking up spent brass at the range and framing someone" and "revolvers" aspect of this.
 

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...call me an idiot...but lets see here...I rack the slide back on my Glock or Walther or any semi auto, I see the bolt face. I also see a rusty nail sitting next to it. I pick it up and scratch the bolt face. I have vastly changed it. I am off scott free? Not to mention what I have mentioned before, with respect to the "picking up spent brass at the range and framing someone" and "revolvers" aspect of this.
Ahhhh, very good padawan.

Yes, you can alter your bolt face. And you can replace the barrel while your at it. This way, niether the breech face impressions or the bullet striations will match the evidence. You are a cunning criminal indeed. But your greatest mistake is revealing your secret here.

Next time you get a chance, ask a policeman if criminals are getting smarter. The responce I've got is, 'not really'.

Now, spent brass at the range is interesting. A good juror should judge evidence by how it connects to the suspect, and how it connects to the crime. One of the factors is the portability/permanence of the evidence. So, DNA evidence from a cigarette butt at the scene is not as good as a DNA from a blood trail. In mock trials, studies show that jurors recognize this.
 

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Discussion Starter · #8 ·
Ahhhh, very good padawan.

Yes, you can alter your bolt face. And you can replace the barrel while your at it. This way, niether the breech face impressions or the bullet striations will match the evidence. You are a cunning criminal indeed. But your greatest mistake is revealing your secret here.

Next time you get a chance, ask a policeman if criminals are getting smarter. The responce I've got is, 'not really'.

Now, spent brass at the range is interesting. A good juror should judge evidence by how it connects to the suspect, and how it connects to the crime. One of the factors is the portability/permanence of the evidence. So, DNA evidence from a cigarette butt at the scene is not as good as a DNA from a blood trail. In mock trials, studies show that jurors recognize this.
Hahaha I was going to say if it was extractor or firing pin marks those things are easy to change, but I forgot about the bolt face marks.

But most gun's are pretty simple to replace parts on.
 
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