Scott Walker, 27, attacked John Brightwell and stabbed and killed his partner Debra Larn in September 2006, Nottingham Crown Court was told.
The court heard he first had contact with mental health services when he was 17 and had turned to alcohol and drugs.
Mr Walker, of Beaumont Leys, denies murder and wounding with intent.
'Violent outbursts'
Only 10 hours before the incident, five-month-old Cadey-Lee Deacon was mauled by two rottweilers at the Rocket public house on Stephenson Drive, Leicester, in an unrelated incident.
Nirmal Shant QC, prosecuting, told the court earlier that Mr Walker had visited the couple to console them about the death of the baby but fuelled by a combination of alcohol and drugs, his behaviour then became "increasingly abusive and aggressive".
He fetched a knife from the victims' kitchen and used it to stab Mr Brightwell, 50, and, fatally attack Miss Larn, 47, the court heard.
Dr Jeremy Kenney-Herbert, a consultant forensic psychiatrist, told the court that the defendant had been diagnosed with an personality disorder which made him prone to violent outbursts.
He said Mr Walker had complained to doctors in the weeks leading up to the stabbings that he was suffering feelings of anger and violence.
He added that the personality disorder was aggravated by substance abuse.
Mr Walker has told the court that he cannot remember the attack.
The trial continues.
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