• It was possible further tests on the shirt's stains could result in no brain matter being detected, but a forensic scientist did not expect that to be the case
• Variations in tests run on biological matter were inevitable
• Results were not gathered from one marker but were a joint interpretation of markers pointing to the presence of brain tissue
• Central nervous system tissue was observed on one of the two marks found on Lundy's shirt
Painstaking analysis of how complex forensic tests were undertaken on Mark Lundy's stained polo shirt dominated the evidence given in court today.
Forensic scientist Laetitia Sijen from the Netherlands Forensic Institute has been questioned since yesterday in the High Court at Wellington over tests that found central nervous system tissue on a mark on the shirt.
The Crown case was that the brain matter was likely to have come from Lundy's wife Christine.
Lundy, 56, has denied murdering his 38-year-old wife and 7-year-old daughter Amber in their Palmerston North home on August 30, 2000.
Under cross examination by defence lawyer David Hislop yesterday, Dr Sijen was asked about data that showed errors in the institute's work.
Dr Sijen said the errors were low compared to the number of tests conducted.
Today, she further clarified that some of those errors were administrative and included typing mistakes.
"It is about learning from your mistakes and many of those mistakes are seen and handled before the report goes out."
Mr Hislop also questioned Dr Sijen about the accuracy of the tests and suggested results might change to show no brain tissue if further tests were conducted.
Dr Sijen said there was no guarantee that wouldn't be the case, but based on the results of the tests conducted, she still expected the brain cells would still be observed.
She accepted there was variation in results - "that is just biology" - but said the institute followed the same methodology and standard operating practices to maintain consistency.
By conducting a certain number of tests, the result would come from "joint interpretation" of the markers that indicated the presence of brain tissue, she said.
Dr Sijen worked with RNA, which told her which part of the body cells came from - different to DNA which would indicate who the cells belonged to.
Defence lawyer David Hislop said one of the criticisms regarding one of the tests was that unequal amounts of RNA was used in the test compared to the control sample.
"I do not fully understand that because in my view there are good reasons to use less," Dr Sijen said.
Mr Hislop said by "playing around" with the quantities on either side of the scientific experiment she was comparing apples with lemons.
"I don't think you are comparing apples with lemons - maybe you take a smaller lemon and a bigger lemon," she said.
The trial in front of Justice Simon France continues.