This police photo released by the Connecticut Judicial Branch as evidence presented Thursday, Sept. 29, 2011 in the Joshua Komisarjevsky trial in New Haven, Conn. Superior Court shows the fire-damaged kitchen in the Petit home in Cheshire, Conn., where three family members were killed during a home invasion July 23, 2007. (AP Photo/Connecticut Judicial Branch)

NEW HAVEN, Conn. - A Connecticut man charged with a gruesome home invasion had gas on his boots, pants and sweatshirt, a state lab official testified today, potentially undermining defense efforts to blame a co-defendant for dousing the house in gas and setting it on fire.

Joshua Komisarjevsky had gas on his clothes, testified Jack Hubball, a chemist at the state forensic lab. Komisarjevsky has blamed Steven Hayes, who was convicted last year and is on death row, for pouring the gas.

Michaela Petit, an 11-year-old girl who was killed in the fire along with her 17-year-old sister, Hayley, had bleach on her shorts, Hubball said. Komisarjevsky is charged with sexually assaulting the girl. Hayes' attorney said during his trial that Komisarjevsky had poured bleach on her clothes to try to eliminate his DNA.

The girls and their mother, Jennifer Hawke-Petit, who was raped and strangled, all had gas on their clothes, Hubball said.

Authorities say Komisarjevsky and Steven Hayes broke into the Petit family's home in Cheshire in July 2007, beat Dr. William Petit with a bat and tied him and his family up. Hayes was convicted of strangling Hawke-Petit and killing the girls, who died of smoke inhalation.

Under cross-examination, Komisarjevsky's attorneys noted he did not have gas on the gloves he wore and suggested the fuel could have come from construction work Komisarjevsky did.

A judge denied a defense motion for a mistrial Monday after a supporter of the victims' family spoke to jurors in the trial.

The juror says a member or supporter of the Petit family commented Friday during the lunch break, saying "thank you for doing what you're doing." The judge then questioned the jurors about what was said and how it affected them.

Two alternate jurors were nearby but said they didn't hear the comment. None said the comment affected his or her ability to serve impartially.

Judge Jon Blue called the comment improper but not catastrophic.

Walter Bansley, Komisarjevsky's attorney, noted he had sought unsuccessfully to have the trial moved out of New Haven. He said the comment was aimed at influencing jurors.

"This just highlights the extraordinary pressure that surrounds this case," Bansley said.

He said the defense has had difficulty getting witnesses to cooperate because of perceived and actual intimidation. Bansley said a defense supporter was approached on the first day of the trial by a Petit family supporter who said: "How dare you support him. You disgust me."

A defense witness had a dead mouse left in his mailbox, Bansley said. He also said members of lawyers' families have been threatened.

"It's this atmosphere that permeates the whole trial," Bansley said. "It's certainly clear to the defense Mr. Komisarjevsky cannot get a fair trial."

Blue said the comment to the jurors was a compliment and not a threat.

He warned he would ban anyone from the court if they approach jurors.

Johanna Chapman Petit, aunt of the two girls killed, said she wasn't sure who approached the jurors but was sure no family member did. She said she didn't think anyone was trying to influence jurors.

Prosecutors are expected to rest Monday in their case against Komisarjevsky, who faces a possible death sentence if convicted.