Last week, Milanese authorities found Leonardo Notarbartolo, the man accused of masterminding the world’s biggest diamond heist, in possession of approximately 2.2 pounds of rough, uncut diamonds.

Many of the stolen diamonds were never recovered, and Notarbartolo was detained for driving around with hundreds of diamonds stashed in his BMW, just a few months after being released from prison for the crime.

Case closed? Not so fast.

Due to the slippery nature of rough diamonds — and of Leonardo Notarbartolo himself — the alleged criminal mastermind could walk away scot free, with the confiscated diamonds back in his possession.

Ever the charmer, Notarbartolo claims he purchased the diamonds legitimately for a mere 10,000 euros, as he told Wired’s Joshua Davis last week through an intermediary. (Davis wrote about the heist in March.) On Monday, the alleged jewel thief contacted Davis again to say that the confiscated diamonds are not precious jewels, but rather industrial-grade diamonds used to manufacture cutting tools, which is why he paid only 10,000 euros for the whole pile.

“Notarbartolo is saying, ‘These are my diamonds. I got them legitimately. Give them back.’ And he’s hired a lawyer, Basilio Foti, to advocate for the return of the diamonds,” explained Davis.

Notarbartolo’s defense will likely hinge on the fact that rough, uncut diamonds are nearly impossible to trace. Polished diamonds typically have certified identities that accompany them during transport, and often contain laser-etched logos or certification numbers that are invisible to the naked eye.

A rough diamond, on the other hand, is pretty much a rough diamond. Because they’re soon to be cut and polished, which changes their characteristics, they’re not certified by the industry. “To say with certainty that any rough diamond is the same rough diamond that was in a vault six years go is almost impossible,” explained Davis, who has reported extensively on the diamond trade.

Despite the fact that the vast majority of the diamonds stolen six years ago were in rough form — and that the guy proven to have organized the crime was just found with a big pile of rough diamonds — authorities probably lack sufficient evidence to put Notarbartolo back behind bars, due to the early-untraceable nature of unpolished stones. Most likely, they will be forced to return the jewels to the convicted jewel thief and send him on his merry way.

“I don’t understand the Italian legal system, of course,” explained Davis, “but speaking on purely logical grounds, if you can’t prove that the diamonds are stolen, then you would logically have to give them back.”

In other words, Leonardo Notarbartolo, who famously liberated $120 million in diamonds and cash from a bank so “secure” it didn’t even need live security guards, may finally have found a suitable second act: freeing himself after being caught red-handed, six years later, with hundreds of what could very well be the very same diamonds.

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