CHICAGO - A newspaper investigation raises questions about the execution of a man for a 1983 slaying at a Corpus Christi service station.

Carlos De Luna was executed 16 years ago for the fatal stabbing of Wanda Lopez, a gas station clerk and a single mother.

De Luna was swiftly convicted and sentenced to death even though the parolee proclaimed he was innocent. He identified another man as the killer.

The Chicago Tribune, in the first of a three-part series published Sunday, said it has uncovered evidence strongly suggesting that De Luna's acquaintance, Carlos Hernandez, was the one who killed Lopez. Hernandez died in 1999.

Hernandez's friends and relatives, ending years of silence, said the felon bragged that De Luna went to Death Row for a murder he committed.

The case was compromised by shaky eyewitness investigation, sloppy police work and a failure to thoroughly pursue Hernandez as a possible suspect, the newspaper reported.

De Luna's prosecutors maintain the right man was convicted, though the lead prosecutor acknowledged being troubled by some of the new information. A former police detective said he now thinks the wrong man was executed.

No DNA or other conclusive proof of De Luna's guilt or innocence is available. The store did not have a security camera.

The newspaper learned of the De Luna case from a Columbia University law professor who had begun to look into evidence pointing to Hernandez.

De Luna was executed by lethal injection in 1989.