The 30-year-old was arrested in February after being spotted driving a Mini Cooper S in Maxwellton Street, Canal Street and High Road.
The court heard from a witness who said he saw Mr Nutini order vodka in a Paisley bar before driving off.
Mr Nutini denies a charge of drink driving.
The witness, Colin May, told Paisley Sheriff Court he reported the singer to police when he saw him driving a car shortly after leaving DeBeers Bar.
Mr May said he had earlier seen Mr Nutini and a friend ordering rounds in the bar.
He said the singer, who was with another man and woman, ordered one round while the man bought another two.
Fiscal Depute Frank Clarke, prosecuting, asked Mr May: "Were you able to hear what was ordered?"
He replied: "From memory, I believe it was vodka, more than one, but I could not be certain of that."
Mr May was later asked about seeing Mr Nutini in the driving seat of a black Mini at traffic lights on Maxwellton Street and Canal Street in Paisley.
He continued: "I had seen him drinking at the bar having more than what would be the legal limit of one to two drinks.
"At first I was a bit thrown and continued my journey home, then I called the police to tell them what I had seen."
Cross-examined by defence agent Massimo Franchi, Mr May was asked: "He goes back to his table and you don't know what happens, those drinks could have been spilled, you don't know?" Mr May agreed.
Mr Franchi put it to the witness: "You don't know if he drank vodka or soda and lime?"
Mr May replied: "I heard vodka being ordered."
When pressed by the sheriff if he could say what Mr Nutini was drinking, he answered: "No I can't."
The trial continues.
Singer Paolo Nutini has gone on trial accused of driving under the influence of alcohol while more than twice the legal limit in Paisley.