A lawyer told the state Supreme Court yesterday that his client’s death penalty case was the weakest one ever to go before the high court, alleging that the jury was biased and that key evidence was improperly withheld from the trial.

Justices heard the appeal of former Torrington resident Eduardo Santiago, 31, who prosecutors say agreed in 2000 to kill a West Hartford man in exchange for a pink-striped snowmobile with a broken clutch. He was sentenced to death by lethal injection in 2005 after a jury convicted him, despite no clear evidence that he was the one who pulled the rifle trigger.

Two other men are serving life prison sentences for the killing of Joseph Niwinski, 45, who was shot in the head while sleeping in his home.

Santiago’s lawyer, Assistant Public Defender Mark Rademacher, told the Supreme Court that there was no way a reasonable jury could have condemned Santiago. The defense presented 25 mitigating factors, including Santiago’s troubled childhood, for jurors to consider against the death penalty, while the state based its argument for execution on one aggravating factor, that Niwinski was killed in a murder-for-hire plot.