SAINT JOHN, N.B. -- A forensic computer expert says while the last recorded activity by Richard Oland was at 5:39 p.m. on the day he was killed, the New Brunswick businessman could have been using the computer for hours after that.

Defence lawyers asked Geoffrey Fellows to examine the data from three computers in Richard Oland's office in Saint John where the body of the 69-year-old businessman was found on July 7, 2011.

Dennis Oland has pleaded not guilty to a charge of second-degree murder in the death of his father.

Earlier in the trial, a Crown witness said the last activity on Richard Oland's computer was at 5:39 p.m. on July 6, 2011, when Dennis was visiting his father to talk about genealogy.

But Fellows told a Court of Queen's Bench jury on Monday that while there is data created when a program or browser is opened on a computer, there is no evidence when most programs or browsers are closed.

He said the last activity shown on Oland's computer on July 6, 2011, was opening of the website for the South Ocean Racing Conference, a yachting website.

It could have been open after 5:39 p.m. to read or even scroll up and down without any evidence of activity being created in the computer, said Fellows, a former police officer who does forensic computer analysis in England.

"Would human interaction be required to close the browser?" defence lawyer Alan Gold asked.

"Yes," Fellows replied.

Fellows said Adobe Acrobat Reader had also been opened at 5:28 to view a document, but it's not possible to say when the program was closed.

Under cross-examination, Crown prosecutor Derek Weaver suggested the programs could have been shut down just a second later. Fellows agreed, but added they could have also been open 10 to 12 hours until the next morning.

The Crown has said Dennis Oland was the last known person to see his father alive and have used the time of the last computer activity in an effort to determine when Oland was killed.

The defence asked Fellows to examine a full week of data from three computers in Oland's office and he determined that the last activity each day ranged between 4 p.m. and 6:30 p.m. Fellows warned that the data can be unreliable because it is constantly being revised and over-written.

Court has heard that Oland suffered 45 blunt and sharp force wounds to his head, neck and hands. His body was found face down in a pool of blood on the floor of his Canterbury Street office.

Dennis Oland is expected to testify in his own defence later at the trial, which is in its 12th week.