Posted: 12/13/2004 7:05:02 PM EDT
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After watching CSI and similar shows on TV once or twice, I'm curious as to how (in detail) law enforcement can figure out from what firearm a bullet was fired? Do they determine it from the bullet, or from the casing, or possibly both? |
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not much detail, but my understanding of it. 1) by serial number there should be a "birth certificate" or the like reported to the BATFE for every gun manufactured and which distributer or FFL holder it went to 2) the distributer or FFL holder keeps yellow forms (4430?) on every gun sold to another dealer or individual. 3) If sold to another dealer, repeat (2) until you find a paper trail from a FFL holder to individual 4) BATFE contacts individual possibly, either thru politeness or no knock raid. 5) individual should be wise enough to have a paper trail to Cover His/Her ass if the firearm is sold later on. Either go thru a FFL dealer, report the gun as legitimately stolen, inherited, whatever. 6) State laws kick in, depends which state you live in - gun is registered via serial number, make model, etc 7) If a gun is recovered from a crime scene, then bullets are fired and put in a ballistics database - recently guns are shipped to some states ship guns with fired casings explicitly so those states can put the fired casings in their ballistics database. 8) Forward trracing (1-5) takes place 9) if 8) fails then tracing via ballistics data, fingerprints, DNA is used to match the gun against known ballistics data, fingerprints, DNA recovered from previous crime scenes. Previous crime scene guns are attempted to be traced via 1-6 above. - if you ever apply for a CCW permit, or the military, FFL, or been arrested, your fingerprints are on file! So repeats the cycle. |
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If they have the weapon, they determine if it is a match by markings on the case, and the bullet also. Each rifle will leave specific extractor, firing pin, and chamber marks on the brass, as well as the usual lands and groove marks on the bullet its self. Without the weapon, usually weapon type and in some cases manufacture can be determined using the same evidence. |
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If you can recover a bullet that has not been deformed too much, you can compare the "marks" left on the bullet from the lands and groves from the barrel. Most barrels will leave a distinct mark, just like tool marks, they can be comapred to "known" sources and a positive match made, kind of like a finger print, tire print, and shoe print, all will generally leave specific charastics unique to the only source. Many ammo makers use unique bullets that, although not always a given, may lead to a specific brand of ammo. An example would be the Nosler Ballistic Tip bullet. If recovered, it could be from a handloaded round or a commercial source as some, like Federal, use these bullets. I would also suspect that trace evidence from the powder residue deposited on the bullet could also be analyized and traced back to a "factory blend" of powder not used by the general public. The same can be said for brass. I'm sure a lab could tell if a factory case has been re-sized in a die and the factory primer replaced. Lastly, the primer strike can be linked back to a specific weapon. Just like every other type and class of "tool marks", a firing pin will leave a distinct impression unique to a specific weapon. Trace the bullet to the case, the case to the gun, verify the bullet to the barrel of said gun, track down the original owner, and who he/she may have sold the weapon to, and there may be a suspect at the end of this trail. The thing to remember about a barrel is the marks it leaves on a bullet can /will change over time as the weapon is fired and cleaned. |
Assuming all they have to work with is the bullet, they can determine caliber, weight and even make of bullet. By examining riflings on bullet, they can determine weapon type, they may not be able to zero it down to a specific model gun, but to a list of suspects. This much work is rarely done though. |
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BATFE has no records of firearms sales other than NFA or stolen firearms. If they trace a serial number, "guns before 68 were not required to have serial numbers" They contact the manuf. they have records to the distributor, "except for Olympic Arms who has a fire destroying records every few years" the distributor has sales record to a gun dealer, he has a record of who he sold it to, once it goes private the chain is broken and the trace is lost. Even if it goes back into a FFL dealer it is lost as without a continuous trail it can not be followed. |
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So BATFE only has ballistics data on NFA rifles? The serial number trace makes sense, I was more interested in the specific methods LE uses to go from either non-deformed bullet and/or casing to a specific weapon match. Seems like, unless they had data on file to find a specific match or if they had some lead by which a weapon was found, all that LE could determine from a bullet or a casing would be caliber, weapon type, and maybe manufacturer. Are the marks left on the brass unique to every firearm, or are they unique only within a particular type of weapon (e.g. Bushie AR-15s are the same, 1911 .45s are the same, etc)? |
They are not unique like fingerprints. Guns with Polygonal bores (glock, hk), are often very hard if not impossible to distinguish. |
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Good question. I, too, would like to see a definitive answer on this subject, esp when it comes to this "database". At what level is it being established, state or fed level?? Or just by the individual manufacturers? Is this voluntary by the manufacturers or mandatory. I heard that Glock keeps a spent casing and bullet from every firearm, while Kimber, for example, just sends along a fired casing to those states where their law requires it. I also thought that the states that require this only require it for pistols, not long firearms. Thanks in advance for any clarification. |