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One unfired bullet.

For now, that’s all the evidence public is permitted to know about that links Richard Allen to the scene where the murdered bodies of Abigail Williams and Liberty German were found.

There may be much more evidence that puts Allen at that spot, but the .40 round is all that’s mentioned in the probable cause affidavit released Tuesday afternoon.

The affidavit says the bullet was found within two feet of one of the girls. And without explaining why it attempted to link the bullet to Allen, the affidavit also says “The (Indiana State Police) Laboratory determined the unspent round…had been cycled through…Allen’s SIG-Sauer P226.” In other words, investigators believe the bullet had been loaded in the handgun, and ejected unfired.

That action leaves unique marks says retired IMPS Det. Sgt. Gregg Arkins, “When you pull back on the slide, the extractor grabs ahold of the round and the extractor is made of hard metal where the shell casing is made of slightly softer metal. So, it leaves very unique microscopic scratches on the shell casing.”

According to ATF, a similar examination of spent shell casings helped Detroit Police link a pair of shootings and led to the murder conviction of Deandre Auston in 2018.

Arkins, a 42-year veteran of IMPD, says in his opinion the ejection mark matching method used in the Allen case is a very reliable law enforcement tool.