The big picture: One of the arguments people make against cryptocurrency is that the difficult-to-trace nature makes it the preferred currency among criminal elements. But engaging in illegal activities on the dark web and using bitcoin for payment doesn't mean you're immune from being caught, as two people recently discovered.

As per a Europol alert, an Italian man has been arrested on suspicion of hiring a hitman on the dark web. The assassin was contacted through a site specializing in murder-for-hire services and paid around 10,000 Euros (~$11,870) to kill the suspect's ex-girlfriend.

In working with the Italian Postal and Communication Police, Europol discovered the plan, and the agency "carried out an urgent, complex crypto-analysis" that allowed it to trace and identify the crypto exchange from which the suspect bought his Bitcoin. The unnamed Italian crypto service provider gave authorities more information on the suspect, leading to his arrest.

ZDNet notes that law enforcement groups are creating new, more advanced tools for tracking and tracing cryptocurrency movements. Interpol is developing Darkweb Monitor, which can gather criminal activity on the dark web, including cryptocurrency addresses. It also helped develop a blockchain-based analytics tool called GraphSense, which allows investigators to search cryptocurrency addresses, tags, and transactions.

In the US, the perpetrator of another attempted murder that utilized the dark web and Bitcoin has been jailed. The DoJ announced that 46-year-old Columbia, Missouri, resident Jason William Siesser was sentenced to 12 years in federal prison without the possibility of parole.

Siesser paid $150 in BTC for around 30 milliliters of Dimethylmercury, a chemical weapon that theoretically could have killed up to 300 people. He planned to use it to kill his ex---just a few drops on the skin can be fatal---but failed to acquire any of the substance on two attempts and was caught in an undercover FBI operation.

"Siesser had been the custodial guardian of two minors and had used various combinations of the first, middle and last names of one of them on the orders for the toxic substance," writes the New York Times. "The youth said Mr. Siesser had told him that he wanted to be an assassin and kill those who had wronged him in the past, including Mr. Siesser's ex-wife and the woman who broke off her relationship with Mr. Siesser after three dates, according to the affidavit."

Image credits: Lubo Ivanko, Motortion Films