Just spitballing here, but I assume that when you cycle a round through the chamber, then eject it even without firing it, it will still get a unique mark on the casing or the bullet itself

But definitively unique compared to the thousands and thousands of other identical Sigs out there?

That seems to push belief.

Or, if not, what am I missing?

---

Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
--

Seems so, per Wikipedia entry on firearm forensics:

Quote:

The examination of the cartridge relies on the unique tool marks left by the various parts of the weapon including the firing pin and the ejector in semi and fully automatic firearms. These markings can be compared and matched to known exemplars fired from the same weapon using the same parts.[29]: 151  The examination of the marks left on the cartridge is done using a comparison microscope. Examiners view the questioned cartridge and the known exemplar simultaneously, looking for similar microscopic marks left during the firing process.[29]: 152 

Edit: Obviously the firing process doesn't apply, but marks from an ejector would. I don't know the statistical rigor involved. But I imagine if it's been used in court, that angle has been challenged to the nth degree by defense attorneys.

it's also possible that the round was subject to a failure to fire. so the firing pin struck, round failed, slide was racked and round ejected, and then a new round was put into the chamber.

(i feel like the article would've mentioned the "failure," but maybe not)

Definitively? Probably not. Almost all of firearms forensics isn't definitive despite TV ;)

You can tell which magazine the cartridge was loaded into. You can tell which gun the cartridge passed through even if it wasn't fired. All the marks on the brass are from that process (except the impact location of the firing pin)

Yeah, that is why I was asking. I know tons of stuff presented and supported in US courts is totally junk science, so I was wondering if this fits in that category.

---

Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
--

Not saying this is the same style gun used but the movement of the bullets would be pretty similar across semi-automatic platforms. The bullets have a few movements when going from the magazine to being chambered. I imagine there would be some markings on the bullet from the slide catching and sliding across the feed ramp. Also thinking about where residue builds when cleaning. The bullet would have had numerous opportunities to pick up residue along the way.

This is the Abby and Libby murder in Delphi Indiana in February 2017. I grew up there, I've been on the trail, and I went to school with many of the people involved in this investigation.

What that article is discussing is the Probable Cause Warrant, and it is redacted. In Indiana that document doesn't need to list all the evidence, just enough to get a judge to sign the arrest warrant. There is a lot more evidence than just the ejected shell.

The prosecutor actually said in one of the court appearances that they have reason to believe others are involved. Until that is sorted out the public is not going to get the entire story.

---

"...the street finds its own uses for things"