Cop quizzed on hammer tests
2007-02-19 16:44
Cape Town - A test used to detect blood also reacted to a variety of other materials, including metals, paints and cleaning products, a police forensic expert told the Cape High Court on Monday.
However the substance, luminol, was used only as a screening test, Peta Davitsz testified in the trial of suspected hammer murderer Fred van der Vyver.
Van der Vyver is accused of bludgeoning to death his student girlfriend, Inge Lotz, in her Stellenbosch flat in 2005.
Davitsz, who gave evidence last week, was recalled to the stand on Monday for further questioning about the luminol test she applied to an ornamental hammer that police took from Van der Vyver's bakkie after the murder.
She conceded, under questioning from Van der Vyver's advocate, Dup de Bruyn, that luminol reacted to a number of substances other than blood.
For this reason, she could "only presume" that the substance that was shown up on the hammer by the luminol was blood.
'It was blood'
However the colour, intensity and duration of the reaction - luminol glows in a darkened room when it reacts in a test - indicated that it was blood, rather than something else.
For this reason, she sent the hammer for further forensic tests.
She said police forensic staff were trained to recognise reactions that were not blood.
Challenged by De Bruyn on a statement on what he said was a scientific website that luminol should not be used as a "presumptive test" for blood, Davitsz reiterated that she had used it as a screening test.
She added that blood was the only reactive substance that showed luminescence when the test was repeated.
Luminol, also known as 3-aminophthalhydrazide, was developed in Germany in 1937, and was initially used to help miners find copper deposits.
Witness flies in
It reacts with the iron found in blood.
The trial was postponed to Tuesday morning to allow the State to consult with its next witness, the pathologist who examined Lotz' body.
She is Dr Ansie Adendorf, who is working in Britain and who flew in to Cape Town at the weekend for the trial.
- SAPA