A mob hit man, a Roman Catholic priest and a violin are taking center stage in a Chicago courtroom where a federal trial is beginning on Wednesday.

Former prison chaplain Eugene Klein is charged with trying to help imprisoned Chicago mobster Frank Calabrese Sr recover what they believed was a 250-year-old Stradivarius violin hidden by Calabrese years earlier in his then Wisconsin summer home to keep the government from selling it. They believed it was worth as much as $26m.

Prosecutors say the plot was hatched in 2011 when Klein, now 65, was administering communion to Calabrese at a prison in Springfield, Missouri. Calabrese was sentenced to life in 2009 for 13 murders, including by strangling some victims with a rope and slashing their throats. He was also ordered to pay $4.4m in restitution. He died in a federal prison in North Carolina in December 2012, aged 75.

After Calabrese’s imprisonment, federal authorities continued to search for his assets. Prosecutors say the longtime Chicago Outfit enforcer wanted to ensure that agents could never get hold of the violin that once belonged to entertainer Liberace, saying he would rather the priest profited from its sale.

According to prosecutors, Calabrese at one point passed a note to Klein – wrapped in religious materials – through the food slot of his cell. It allegedly directed Klein to look in a second-floor bedroom, behind a pull-out door and against a wall in the home in Williams Bay, Wisconsin.

“That is where the violin is,” the note says, according to court filings.

Prosecutors say Klein even called a real estate agent selling the Wisconsin home, posing as a potential buyer. The plan was for another unnamed conspirator to distract the agent during a tour of the home while Klein and another person retrieved the violin.

A federal search in 2010 did turn up a million dollars in cash in a wall behind a family portrait in Calabrese’s Chicago-area Oak Brook home. But despite searches at the Wisconsin home, no violin was found.

Klein is charged with conspiracy to defraud the US and attempting to prevent the seizure of Calabrese’s property. Klein, who is free on bond, has pleaded not guilty. If convicted, he faces up to a decade behind bars.

In the Oak Brook search, prosecutors found a certificate indicating the violin may have been a less valuable one made in 1764 by Giuseppe Artalli, and not by the renowned Antonius Stradivarius. Calabrese seemed confident the violin was a Stradivarius.

At the time of Klein’s indictment in 2011, defense attorney Thomas Durkin criticized the then US attorney in Chicago, Patrick Fitzgerald, whose office indicted and convicted former Illinois governor Rod Blagojevich for corruption.

“Having run out of governors to prosecute, [he] has now decided to prosecute the clergy,” Durkin told reporters. “Apparently he couldn’t find any rabbis or nuns, so today we have a priest.”