FDNY investigators say the suspect deliberately discarded a lit cigarette into cardboard boxes, causing them to ignite.
Prosecutors say Asif Qureshi hid in his estranged wife's home in Herricks in October and waited until she was alone before poisoning her with cyanide.
Nick Reiner's defense attorney, Alan Jackson, withdrew from the case during Wednesday's court appearance.
Officials say the 23-year-old victim was filling in for a co-worker at the cash register that day.
Ashlee Buzzard has been charged with murder with special allegations in the shooting death of her 9-year-old daughter Melodee Buzzard, according to court documents.
Hasseem Jenkins, 32, was convicted Wednesday on charges including second-degree murder, manslaughter and robbery, in the death of Maria Coto last year.