Three decades ago, Chicago mobsters Arthur Rachel and Joseph Scalise were convicted and sentenced to serve 14 years in a British prison for stealing the Marlborough Diamond from a store in London. The 45-carat diamond has yet to be recovered.

After their prison release, the two allegedly reunited back in Chicago to plan other heists at banks and jewelry stores, according to federal authorities. The mobsters and another accomplice were later charged with conspiracy and racketeering, both federal crimes, after authorities discovered that the individuals were plotting to rob an armored car.

Last week, Scalise and the other accomplice both pleaded guilty to the charges. However, Rachel, who is now 73 years old, pleaded not guilty which prompted his case to go to trial. On Thursday, he was convicted of three of the four counts filed against him in the federal criminal case.

Some speculate that Rachel may have pleaded not guilty in an effort to use his old age to his advantage during the trial. According to ABC 7 Chicago, the mobster's attorney argued in his closing statement that the prosecution failed to prove beyond a reasonable doubt that his client committed the crimes.

But instead of convincing the judge to acquit Rachel, the judge only acquitted the mobster of one weapons count and convicted the elderly man of three other counts.

During the trial, prosecutors argued that even though Rachel is 73 years old, that does not make him incapable of hurting others. Since the alleged plot to rob the armored car included the use of weapons, prosecutors argued that the mobster would have used the weapons against others in order to execute the heist.

Source: Chicago Tribune, "Aging reputed mobster takes a chance with trial and loses: Guilty of racketeering," Annie Sweeney, Jan. 26, 2012