PROSECTORS have failed to produce a motive for a murder accused to have set a fatal blaze, it was claimed in court.

Three members of the same family were killed when petrol was poured through the letterbox of their home in Helensburgh, Argyll and Bute, and set alight.

Scott Snowden, 37, and Robert Jennings, 50, deny starting the blaze on July 24, 2011.

At the High Court in Glasgow, Snowden's defence counsel told the jury that no motive for the attack had been proved during the trial.

Donald Findlay QC said that drug dealer Snowden had not been banned from a bar owned by victim Thomas Sharkey as suggested by the Crown.

He said no commercial rivalry had been proven between the pair.

Mr Findlay said: "The reality is that, try as they might, the Crown has produced no motive. The Crown's attempts to produce a motive have failed."

Mr Sharkey's eight-year-old daughter Bridget and his son Thomas junior, 21, died in the fire at Scott Court. The 55-year-old father died in hospital six days later.

His wife Angela, 48, survived.

Advocate Depute Alex Prentice said in summing up the case that Snowden had "instructed or instigated" the fire to be carried out.

Mr Findlay said today there was not a "single jot" of evidence incriminating him.

Jenning's defence counsel Ian Duguid is expected to address the jury tomorrow before the panel is given directions by judge Lord Matthews.

Mr Findlay suggested that there was a list of people with motives to set fire to the Sharkey home, among them several Crown witnesses and members of the Sharkey family who he said had lied to save their own backs.

He told the jury: "Does anybody have a motive to do Thomas Sharkey harm? Start where you like.

"You have a list of people, through various members of the Sharkeys themselves, who have a real issue, a real anger... a real hatred of Tommy."

Mr Findlay described the Crown case as a cable made up of strands, many of which were weak and may not stand up to stress put on them.

Concluding his argument, he said jurors were standing before a bridge.

He said: "It's a bridge that is supported by a cable.

"This cable has become weaker and weaker, I suggest, and now individually and collectively we have a choice.

"You can step on the bridge and walk across as the Advocate Depute said you should.

"If you think 'that's too dangerous for me', that's the end of it and you acquit Mr Snowden of the charges.

"If you think 'it's not safe, I might not make it', acquit Mr Snowden.

"Please, ladies and gentlemen, don't take a risk just because you feel somebody should be made to pay."

The trial continues.