The 33-year old funeral director was found guilty by the jury of eight men and seven women at the end of a five day trial at the High Court in Edinburgh.
Lockhart strangled his 28-year old wife, Janet, and smothered his two-year old son, Michael, in the family home in South Chesters Lane, Bonnyrigg, on December 28 last year.
Defence solicitor advocate Brian Gilfedder had offered a plea of guilty to murder in respect of Mrs Lockhart, but not guilty to his client’s murdering his son, claiming Lockhart been suffering from diminished responsibility due to an abnormality of mind and that he would plead guilty to a reduced charge of culpable homicide. This was rejected by the Crown.
During the trial the jury heard how Lockhart had returned home at 2am after a night of heavy drinking. His blood alcohol level was three times over the drink drive limit.
His wife, Janet, was due to go to work at 4am and was concerned that he was in no fit state to look after Michael if he woke. There had been an argument and he strangled her.
After sitting beside her body for a while, he went upstairs to the main bedroom.
He told the court: “I could not believe it happened. I didn’t believe it was real”.
He explained that he believed in reincarnation and the after-life and was worried about what would happen to Michael with his mother dead and his father in jail and decided the only solution was to kill his son and then commit suicide.
Consultant Forensic Psychiatrist, Dr Andrew Wells, told the jury that although Lockhart was not suffering from mental disorder or illness, his decision-making appeared to have been substantially impaired and he could have been suffering an acute stress reaction due to his wife’s death.
Addressing the jury, the judge, Lady Wise told them there was only one verdict they could return on Charge 1 - the murder of his wife - but on the second charge, they could return a verdict of guilty of murder or culpable homicide. “Acquital is not open to you” she said.
After an hour and twenty minutes, the jury returned a unanimous verdict of guilty to the murder of Janet Lockhart and a majority verdict of guilty to the murder of Michael.
Mr McSporran paid tribute to Janet’s parents and Michael’s grandparents for the dignity they had shown throughout the extremely harrowing evidence in the case.
“It is absolutely plain they simply cannot understand what happened on the morning of December 28 last year and the dreadful events to their beloved daughter and grandson”.
Lady Wise told Lockhart the only sentence for murder was life imprisonment, but she was calling for a Criminal Justice Social Work report to help determine the minimum term he would have to serve.
He will be sentenced on October 16.
Following the verdict, Detective Chief Inspector Scott Cunningham from the Major Investigation Team, who lead the investigation, said: “In 22 years in the Police Service this is one of the most tragic, traumatic and heart breaking investigations I have been involved with.
“The unforeseen actions of Garry Lockhart are completely incomprehensible and only he knows why he took the lives of his wife and son.
“I acknowledge the verdict today and my thoughts first and foremost are with Janet and Michael’s family.
“This has been devastating for the family and I want to pay tribute to them for their strength, courage and dignity shown. I also want to commend all the police officers, police staff, partner agencies and the local community for their professionalism and support throughout the most emotive circumstances.”