ST. AUGUSTINE, Fla. -

A forensic expert called by defense attorneys testified Tuesday in the trial of a St. Johns County man who is accused of murdering his wife for insurance money.

Justin Barber is charged with killing his wife, April, in 2002, but he insists they were both shot by an unknown gunman.

As testimony got under way Tuesday, forensic expert Alexander Jason was called to the stand by the defense. Jason analyzed bullet holes, blood markings and the wounds to Justin Barber, and told the jury the explanation given by Barber about a gunman attacking him and his wife was logical.

"It could be consistent with a struggle. If someone if is fighting with somebody, grabbing their shirt and moving around, that could account for why it would be pulled down," Jason said.

During cross-examination the prosecution countered that despite expert testing, Barber still could have created the gunshot wounds himself.

"I asked you, 'Is it consistent with the defendant shooting himself through that hand?'" France said.

"It could be. Yes," Jason replied.

Before testimony got under way Tuesday, the prosecution and the defense got into a discussion about what the defense said was a harmless accident.

One of the defense's witnesses used a red marker to put marks on a shirt identical to the one Barber was wearing the night of his wife's shooting death to show where he'd been shot. However, the actual shirt was under the shirt the witness was drawing on and the red marker bled through, staining the evidence.

Lead prosecutor Chris France contended the incident was evidence tampering.

"This was not a black or green Sharpie. It was a red Sharpie, and it obscures this evidence," France said. "You just don't touch evidence like this. That's why we put it in evidence."

The judge advised that he would tell the jury what happened and not penalize the defense.

Closing arguments will begin Wednesday morning at about 9, and deliberations are expected to begin Wednesday afternoon.