Chicago ? Chicago police beat, kicked, shocked or otherwise tortured scores of black suspects in the 1970s and 1980s to try to extract confessions from them, prosecutors reported Wednesday.

However, the prosecutors – appointed by a Cook County judge four years ago to look into torture allegations – said that the cases are too old or too weak to prosecute anyone now.

Prosecutors Robert D. Boyle and Edward Egan said they found evidence that police abused at least half the 148 suspects whose cases were reviewed. Nearly all of the suspects were black.

Among other things, the suspects claimed that police beat them, played mock Russian roulette, administered electric shocks with a cattle prod-like device and a crank-operated “black box,” and threw typewriter covers over their heads to make them gasp for air.

The investigators were not able to substantiate all of the allegations, but made it clear they believed many of the claims, and said that in the majority of cases, suspects were beaten with fists, feet or telephone books.

Boyle and Egan said that in only three cases involving a total of five former officers was there enough evidence to prosecute, but the three-year statute of limitations has run out.

“We only wish that we could indict on these three cases,” Boyle said, after a $6.1 million investigation that involved more than 33,300 documents, the issuance of 217 grand jury subpoenas and interviews of more than 700 people.

Attorneys for the alleged torture victims called on Illinois’ chief federal prosecutor to bring federal charges. But Boyle said the U.S. attorney has also concluded that the statute of limitations has run out.