Kissel, 41, had earlier told the court that Robert Peter Kissel had beaten her with the bat in the master bedroom of their flat in Parkview, Tai Tam, on November 2, 2003, after telling her he had filed for divorce.

She claimed she had used a metal ornament to fend off blows from the bat. Prosecutor Peter Chapman has told the court that Kissel used the 3.7kg ornament to deal five fatal blows to her husband's head after drugging him with a sedatives-laced milkshake.

In cross-examination, Alexander King SC, for Kissel, asked Dr Pang: 'Would you agree that not everyone who touches the end of the baseball bat leaves DNA material detectable to tests?'

The witness replied: 'I can say a light touch with my fingertip on the microphone may not leave my DNA behind. But if I grab it tight and keep moving it here and there, I ... believe DNA would ... be left.'

The defence counsel asked if DNA traces could stay on the bat for six months. Mr Pang said it depended where the article was kept.

'Are you saying that in the history of that bat, only one person has ever held the handle?' asked the counsel. 'I did not say that,' the witness replied. He agreed when asked by Mr King if he was informed by police that the bat would not be tested for fingerprints.

Kissel admits killing her husband, a banker with Merrill Lynch, but pleads not guilty to his murder.

Forensic scientist Wong Koon-hung, another prosecution witness recalled to give rebuttal evidence yesterday, said the ornament was made of almost pure lead, a relatively soft metal that would leave traces even on a piece of paper after contact. 'Therefore I would expect to find some lead smear on the bat had they been in contact. But I found none,' he said.

Neither did he find lead traces on a white pillow case in which the bat was kept for a time after being found in the flat by defence solicitor Simon Clark. The exhibit was handed by the defence to the prosecution in court a month ago for the government laboratory to perform tests.

There were no traces of paint from the bat on the ornament.

'There has also been a suggestion that the curvature of the [ornament] base was caused by impacts of the baseball bat on the base. Did you conduct further tests?' asked Mr Chapman.

The expert said the indentations on the base measured 1.4cm and 1.8cm respectively. Dr Wong said two baseball bats were used in control experiments to hit two pieces of 2kg lead sheet at a 90-degree angle, resulting in maximum indentations of between 1.4cm and 2cm.

The strikes also produced an arc of regular V-shaped curvature on the sheets, with wood grain pattern on the deepest part of the groove. Lead smear was left on the surface of the bats. But the shape of the ornament base was 'too irregular' to have been produced by the impact of the bat admitted as evidence, said the forensic expert.

He was not able to suggest what had produced the indentation shapes on the ornament.

Dr Wong told the court that he could not rule out the possibility the bat had been in contact with the metal ornament. But he said: 'It's conclusive that the piece of metal had not been struck with the baseball bat with significant force.

'To cause that level of damage would require quite a significant force. Under such force, I would expect at least some wood grain pattern pertaining to the bat on the metal ornament.'

In cross-examination, Mr King asked Dr Wong how many pieces of lead sheet he had used. He said he had three lead sheets with him and explained that he had hammered the pieces flat for further tests if he was not satisfied with the results.

The defence counsel said that meant the witness had destroyed results of earlier tests, and argued that any wood grain residue left on the lead sheets when they were struck with the bats could have been hammered out.

Mr King asked for the other lead sheets used in Dr Wong's tests to be brought to court for examination.

The case continues today.