A former soldier accused of killing his grandmother lied when he told partners he had smothered the 84-year-old as a way of getting sympathy, a court has heard.
Barry Rogers, on trial along with his mother Penelope John for the murder of 84-year-old Betty Guy, came under suspicion after one of the three ex-partners he told about being involved in the former nurse's death went to the police.
On Monday at Swansea Crown Court, the 33-year-old, said he initially thought his three former partners had colluded but later realised the details they knew meant he must have spoken to them about it.
He told jurors he did not remember the conversations.
"At times I think that yes, they have all been in contact but realistically no they haven't," he added.
During cross-examination by Paul Lewis, for the prosecution, Rogers said "sometimes I tell the truth" but admitted he told lies to get the result he wanted on occasions.
Mr Lewis said: "The result you want in this case is for the jury to say you had nothing to with your grandmother's death isn't it?"
He said it was but insisted he had not lied to the jury.
Rogers, of Fishguard, Pembrokeshire, and his 50-year-old mother, of St Dogmaels, deny murder and the alternative charge of manslaughter.
John is accused of giving her mother a cocktail of drugs and whisky before Rogers used a pillow or something similar to smother Mrs Guy at her home in Johnston, Pembrokeshire.
The court previously heard John dialled 999 in the early hours of November 7, 2011 to say she thought her mother, who she claimed was suffering from stomach and bowel cancer, had died.
Rogers and John were first arrested four years later after Sandra Adams, who had been in in a relationship with Rogers, went to police.
He was asked about what he told Ms Adams about his grandmother and her having cancer.
Rogers said he did not know if Mrs Guy had the disease at the time of her death and the jury was previously told there was no evidence she did.
Of Ms Adams, he said: "I don't believe I would have (told her). She was a winter warmer, something to get me through the nights, she wasn't a relationship I could see progressing."
Mr Lewis asked: "What possible gain could there be to you to admitting to people that you had killed your nan if you had not?"
The former soldier, who said he suffered from PTSD and "borderline personality issues", said "abandonment is a big issue to me" and that he would tell lies for sympathy.
Mr Lewis asked: "How would you be likely to gain more sympathy by saying that you killed your nan, than by saying I did my absolute best to drive from Somerset to Johnston to see her (but she died)?"
Rogers said his mind "worked differently at that point" but said he was not sure if medical evidence about his various mental health problems would be put before the jury by his lawyers.
Mr Lewis asked Rogers if he helped Mrs Guy to end her life because she was in unbearable pain or if it was mercy killing.
Rogers said it was not.
Police installed covert recording equipment in John's home while they were in custody being interviewed in 2016.
In one exchange, Rogers said to John: "No honestly, you have got nothing to worry about, it's me that's the one that's done the act."
He told the jury he suspected the house might be bugged and warned his mother on the way there.
Rogers added that he was "under the influence of drugs (prescription and cannabis) more or less from the moment we walked back through the door" after being released from the police station.
The trial continues.