Just last week in the Chicago terror trial of Tahawwur Rana, the prosecutor, in telling the jury to believe David Coleman Headley, a former DEA informant with two prior heroin convictions who admitted to plotting the Mumbai bombings that killed more than 160 people and to planning an attack in Denmark, and who escaped the death penalty and extradition to India in exchange for his testimony, told the jury in closing:

“What would you have your government do — tell Mr. Headley, ‘I’m sorry, you’re a despicable person and we’re not interested in what you have to say to us’?

The "hardened criminals" prosecutors rely on every day to get convictions, especially in courtrooms across America, are all being paid, either with money or promises of leniency (and freedom is a commodity far more precious than money.) The "hardened criminals" testifying for Amanda Knox are getting neither.

A prosecutor urging a fact-finder not to believe someone because he or she has a criminal record is laughable. What they really mean is hardened criminals can only be trusted when the Government calls them as witnesses.