David Laffer has officially withdrawn his not guilty pleas to charges of first-degree murder and criminal use of a firearm and waived his right to appeal.
Laffer's wife, Melinda Brady, also pleaded guilty to robbery charges.
The judge announced his intention to sentence Laffer to the maximum of four life sentences with no parole, to be served consecutively, and Brady to 21 to 25 years in state prison.
Formal sentencing for both husband and wife is scheduled for October 17.
Laffer and Brady were arrested June 22 in their suburban home a mile and a half from Haven Drugs, where authorities say he opened fire on the victims before jamming the backpack full of prescription painkillers.
Prosecutors have called the killings, which were captured on a drugstore surveillance camera, "the most cold-blooded robbery-homicide in Suffolk County history."
The four deaths were the worst mass killing on Long Island since a gunman opened fire on a Long Island Rail Road train in 1993, killing six commuters.
The victims included the 45-year-old pharmacist who was working so a colleague could enjoy Father's Day, and a 17-year-old clerk who was days away from her high school graduation.
A 71-year-old man picking up medication for his ailing wife and a 33-year-old mother of two who was planning to be married this year were shot in the back of the head when they unwittingly walked in on the carnage, police said.
LINK: Jaime Taccetta Fund