Allowing a jury to hear evidence of the attempted robbery of a shoe store seven months after a similar crime ended in the torture slaying of a store clerk prejudiced the jurors against Michael DeCorso, an appeals attorney argued Monday.

DeCorso is seeking to have his January 1996 capital murder conviction in the slaying of clerk Margaret Ann Martinez reversed.Attorney Joan Watt argued before the Utah Supreme Court Monday that evidence against DeCorso, 28, in the Martinez killing is circumstantial and letting jurors hear about a similar robbery implicating DeCorso predisposed them to find him guilty.

DeCorso is serving a life prison term without parole in the February 1994 death of Martinez, who was working alone in a West Jordan Payless shoe store. The store was robbed just before closing time, with Martinez bound with duct tape, stabbed and sexually assaulted.

Two clerks from another Payless store in Draper testified DeCorso attempted to rob their store seven months later, hiding in a back room until closing time, then emerging with a gun. But one clerk fled out the front door and the robber ran out the back, dropping a fanny pack.

A fingerprint on a shoebox in the Draper store, along with other prints, matched one lifted off the duct tape wrapped around Martinez and was identified as DeCorso's in the trial.

Introducing that testimony and evidence both confused and prejudiced the jury against DeCorso and forced his attorneys to try and counter it, in effect having to conduct a trial within a trial, Watt told the justices.

There were also not enough similarities between the two crimes to allow the Draper incident to be brought in, Watt said. "There is nothing distinctive about the Draper robbery that makes it relevant to the West Jordan case," Watt said.

Assistant Attorney General Kris Leonard argued there is a long string of similarities and the matching of the fingerprint in the two criminal episodes to DeCorso merits inclusion of the second robbery.

The similarities show "you have a defendant who's found a plan that works and was using it again in Draper," Leonard told the judges. "He picks his time and he picks his place.

"These crimes were committed by the same man."

Leonard also said the jury was "spoon-fed" detailed instructions on how to view the evidence of the second robbery, instructions that were approved by his defense attorney.

The court took the arguments under advisement.