A polo shirt found in Mark Lundy's car had blood on it.

ESR forensic scientist Bjorn Sutherland has told jurors in Lundy's retrial for the murders of his wife and child about the testing he carried out on a polo shirt.

He says chemical testing of two stains on the shirt, showed the probable presence of blood.

Mr Sutherland noted blood in the pocket stain, using a microscope.

"Secondly I tested this area with two different chemical tests for the presence of blood, both of which were positive."

Bjorn Sutherland says he noted a lump of something on the sleeve, and took a slide sample from the stain.

Under cross examination from Lundy's defence lawyer scientist Bjorn Sutherland agreed blood would be spattered onto the assailant.

"I would expect the assailant to have spattered blood on the outer surfaces of exposed clothing and on any other exposed surfaces."

Tiny drops of blood found on Mark Lundy's shirt were found to contain DNA belonging to Amber Lundy.

Bjorn Sutherland was asked if cross contamination from the crime scene could be how the blood detected was picked up on the shirt.

"The polo shirt was examined in the isolation room. This room is used to keep items from separate sources separate."