A computer expert giving evidence on what time he thinks the Bain family computer was turned on on the morning of June 20, 1994, has told the David Bain murder retrial that his findings involved a lot of "guesswork".
Police national manager for the electronic crime laboratory, Maarten Kleintjes, explained to the High Court at Christchurch the variables in the times he used to make his assessment.
In 1997 he cloned the Bain computer hard drive. The technology was not available for previous witness Martin Cox to do this in 1994, to preserve the original data.
He said the hardware clock in the computer was not working as the battery was flat.
The system clock on the computer only runs when the computer is turned on and stops when it is turned off, and when he put a new battery in the hardware clock, the two clocks did not keep accurate time with each other.
When he used the new technology to get a time off the computer, he found out that Mr Cox (the original computer expert to work on the Bain computer) would have only been given a minute time and not the 54 seconds he found on it.
Another variable was the time taken by Mr Cox to do the original work on the computer, as he would have to stop and think through every keystroke he was doing as he was working on live evidence.
The watch used by retired detective Kevin Anderson to write down when Mr Cox was doing anything on the computer did not have a second hand on it, and only had markings for five minute increments.
He said it had a square face and it would depend what angle you looked at it as to what time it told you.
The watch could have been accurate, fast or slow on the day as it was not checked for time until nine days later, and when it was checked with Telecom they only gave the minute time and not the second time, Mr Kleintjes said.
The degree of guesswork has been worked out by different variables for each scenario, and is being explained in detail to the jury. He is continuing to give evidence.
David Bain has been charged with the murders of five members of his family: his father Robin, mother Margaret, sisters Arawa and Laniet, and brother Stephen.
The defence has said the time the computer was turned on is crucial, as David Bain was seen at the gate of his house after his paper round at 6.45am by a neighbour.
The defence has said that if the computer was turned on earlier than this it was not him that turned it on, and wrote the message that was left on-screen, "Sorry you are the only one who deserved to stay".
