A police CCTV analyst told a triple murder trial jury that she was not an expert on how people walk.

DC Jennifer Bell was giving evidence for a second day at the trial of Scott Snowden, 37, and 50-year-old Robert Jennings.

They deny murdering Thomas Sharkey, 55, his son Thomas junior, 21, and his daughter Bridget, 8, at their home at Scott Court, Helensburgh, on July 24, 2011.

DC Bell had earlier told the High Court in Glasgow that she recognised Jennings as the person caught on CCTV cameras in Helensburgh before and after the fatal fire because of his walk which she described as a kind of "shuffle".

She was asked by defence QC Ian Duguid, representing Jennings, if she was an expert in people's gait and said: "In gait analysis, no.

"I don't have any formal qualification, but I have viewed footage over and over again hundreds of times."

DC Bell claimed that when she saw Jennings walking down a corridor in Govan police station she recognised the walk.

Mr Duguid then said: "Was that the only opportunity you had to see Mr Jennings walk in the flesh," and she replied: "It's the only time I have ever met him."

She was then asked if she was watching him from behind and replied: "That's right."

The CCTV, taken at the junction of John Street and West Princes Street on July 24, 2011, which has been shown to the jury many times shows a hooded figure side on.

DC Bell was asked why she was in the cell area while Jennings was being processed and replied: "I was part of a team. I assisted because there was no one else available."

It was suggested by Mr Duguid that female officers were not involved when men who are detained are removing their clothing for analysis.

She replied that Jennings removed his clothing in a cell and she waited outside.

DC Bell said it was when he walked out of the cell dressed in other clothes that she saw him walk down a corridor for a few seconds.

The QC asked why this footage was not shown to the jury and DC Bell replied: "I believe it may have been down to the operator who did not download it properly."

The trial before Lord Matthews continues.