A New York man and his 49-year-old mother have been convicted over the robbing and killing of a "homeless" pensioner after discovering he had a winning lottery ticket.

Robert Pinckney, 66, who was living in a garage after losing his home to foreclosure, thought he had struck gold when he won a scratch-off lottery ticket.

But prosecutors say his luck turned when Jacqueline Staples learned of the win while visiting him in his makeshift home in September 2015.

She called her 29-year-old son, James McCracken, who arrived at the garage in Rochester's Norton Street, a short while later to steal the ticket.

He was then said to have stabbed and beaten Pinckney to death.

The mother and son were later seen at a nearby convenience store to cash in the winning ticket.

McCracken, of Rochester, pleaded guilty on 9 January to second-degree murder, while Staples admitted a robbery charge.

Officials declined to release the amount the winning ticket was worth.

McCracken is due to be sentenced on 13 March to 20 years to life in prison, while his mother will be sentenced the same day to eight years, Associated Press reported.