Joshua Jacques, 29, is accused of killing Samantha Drummonds, 27, her mother Tanysha Ofori-Akuffo, 45, her grandmother Dolet Hill, 64, and Ms Hill’s partner, Denton Burke, 58, on April 25 last year.
Police were called to Ms Hill’s terraced home in Delaford Road, Bermondsey, south London, in the early hours of the morning, finding Mr Burke’s body at the foot of the stairs and the three women in the kitchen.
They all suffered numerous stab wounds with one or more knives and were pronounced dead at the scene.
Tom Little KC, prosecuting, told jurors at the Old Bailey on Monday: “This case involves not one death, not two deaths, and not even three deaths but four violent and brutal deaths at the hands of this defendant.
“In killing four people the prosecution say that the defendant murdered three generations of one family.
“There is no dispute or issue other than that it was the defendant that killed all four of the victims and that he did so by attacking them. He did so by stabbing them, cutting them and slashing them.
In the days leading up to their deaths, Ms Drummonds had shared her concerns over Jacques’ mental state with her best friend, saying that he was having an “episode” and that she was unsure what had “triggered” it.
“What you will have to decide is why he did so and what his state of mind was at the time,” Mr Little KC said.
“The prosecution case is that this is a clear case of murder or more accurately a clear case of quadruple murder.
“We say that the defendant killed his victims with murderous intent, and there’s no dispute about that, and that when he did so his ability to form a rational judgment and to exercise self-control were not substantially impaired by any psychiatric condition and indeed that his conduct on that night was brought about by self-induced intoxication, taking drugs and drinking alcohol.
“This, we say, led to a transient psychotic disorder not meeting the requirements for the defendant to make out a partial defence of diminished responsibility.”
Following their deaths, a GoFundMe page was established to pay for funeral costs with the extended family saying they had been left “truly heartbroken”.
The family said that Ms Drummonds was “an upbeat, fun-loving, bubbly young lady who adored her grandmother Dolet”, while her mother had worked as a nurse and was described as “a doting wife, caring mother and a great friend”.
Hill had been married to Burke, a council worker, for 15 years and had worked in the NHS for more than 20 years as a housekeeper at Guy’s hospital.
Jacques, from Minard Road, Lewisham, south-east London, has pleaded guilty to their manslaughters but denies murdering them.
The trial continues.