William Kean, 46, denies killing Jenny Methven by striking her repeatedly on the head and body with a blunt instrument at Kildinny Farm Cottage in Forteviot, Perthshire, on February 20.
He lodged a special defence of incrimination against her son David Methven or others unknown, who are connected to him, during the first day of his trial at the High Court in Glasgow yesterday.
In a joint minute of agreement between the prosecution and defence, the jury of six men and nine women were told the pensioner died from brain injuries and blunt force trauma.
Kean's bloodied fingerprint was found on a phone in Mrs Methven's kitchen.
It is also agreed by the prosecution and defence Kean touched Mrs Methven's lower right arm on the day she died.
Kean is also accused of stealing around £15,000 from her home on September 14 last year.
Forensics expert Yvonne McLaren told jurors she had examined the crime scene and noted pools of blood on the kitchen carpet and blood spatter and runs of blood on one wall.
The court heard Kean's fingerprint was found on a wall telephone covered in Mrs Methven's blood. Police also found his DNA on a glass and on one of Mrs Methven's arms.
A pair of cords with Mrs Methven's blood on them and with the bottom of one of the pockets cut off were found in Kean's home.
Prosecutor Alex Prentice, QC, asked Miss McLaren: "There may be a number of reasons why someone would cut the end off a trouser pocket," and she replied: "That may be."
He then said: "Would it also allow you to place an item in the pocket. For example if you wanted to conceal a hammer, is that a possibility," and she replied: "It may be."
Defence QC Brian McConnachie asked Miss McLaren: "If William Kean is the perpetrator he has left behind his fingerprint on a telephone, his DNA on a glass and his DNA on Mrs Methven's arm," and she replied: "Yes."
Mr McConnachie added: "One of the things that has been suggested to you is that the removal of part of the trouser pocket is to secrete a hammer," and she replied: "Yes. It is a possibility."
The defence QC added: "The person who has gone to that trouble then effectively left their signature in the cottage ," and she said: "Yes."
Mr McConnanchie said: "The premeditated plan seems to have run out at the point of wearing gloves," and she replied: "Yes."
Miss McLaren agreed that someone who struck wet blood repeatedly would be covered in it.
The trial continues.
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