Mark Lundy retrial: Forensic testing criticised

Mark Lundy has denied murdering his wife, Christine, and daughter Amber in Palmerston North in August 2000. Photo / Mark Mitchell

A German scientist has criticised the method of testing stains on Mark Lundy's polo shirt that found human brain matter.

Research scientist Marielle Vennemann was giving evidence via audio-visual link from Germany at the Lundy double-murder trial in the High Court at Wellington today.

The Crown's case is Christine Lundy's brain cells were smeared on her husband's shirt.

Lundy, 56, has denied killing her and their 7-year-old daughter Amber in their Palmerston North home on August 30, 2000.

Defence witness Dr Vennemann was critical of testing done by the Netherlands Forensic Institute (NFI) that found brain was observed on the shirt and discounted that the matter belonged to an animal.

The methods the institute used were "not fit for purpose", she said.

The NFI studied RNA - which showed where in the body a cell came from.

Dr Vennemann said three tests undertaken by the NFI to find out what species the cells were from had issues.

It was possible to achieve false positive results in the first test in regards to cow, rabbit, rat, mouse and particularly pig, she said.

Results could be identical to Homo sapiens, she said.

In the second test conducted by the NFI, there would have been no chance to distinguish human from non-human in regards to sheep, goat, rabbit, rat and mouse, she said.

The third test showed a similarity to a pig.

During her evidence on the test, Dr Laetitia Sijen from the NFI said similar results were not the same as exact results, therefore the test showed human rather than pig.

But Dr Vennemann said the NFI did not go an extra step to ensure the sample was not pig.

There was also an issue with the number of markers the NFI used to identify brain matter.

The NFI told Dr Vennemann it was okay if one marker out of four was not specific to brain.

"Surely this is a big problem," Dr Vennemann said.