He said as he headed north on High St, he noticed a car coming towards him, weaving across the centre line and into the path of oncoming cars, forcing drivers to take evasive action.
He noticed two people in the car, including the bearded driver. The pair had no time to swap positions, he said in evidence.
"I observed the vehicle wandering and straddling the centre line," he said.
Doing a u-turn, Mr Simpson said, he stopped the car on the outskirts of Carterton and spoke with the driver who was in the driver's seat and intoxicated.
"He refused to give me his name and said he wasn't the driver. He was slurring. He smelt strongly of alcohol and was uncooperative."
Kelly was arrested after being warned for failing to provide his details and failing to undergo a breath test.
At Masterton station, Mr Simpson said he was unable to get a conclusive reading from a breath test and repeatedly asked Kelly to undergo a blood test, which he refused by ignoring him. He had to help Kelly from the patrol car as he couldn't stand up.
"I asked several times. He failed to acknowledge ... he was belligerent, arrogant and intoxicated."
When asked in cross-examination by defence lawyer Ian Hard about Kelly telling him he had taken a pain killer that day and the week previously, Mr Simpson said he was told.
Mr Hard also put to Mr Simpson that his client hadn't refused to give blood and the officer had only determined from Kelly's actions that he was refusing.
But the officer said he had given Kelly ample opportunity to give a blood sample.
"He refused to complete the test ... it took considerable time. I asked him numerous times ... he never stopped being uncooperative."
Sergeant Peter Rix gave evidence stating Kelly appeared drunk and obstructive.
He was definitely under the influence of alcohol, Mr Rix said.
"He was belligerent and difficult, as intoxicated people are. He reeked of alcohol and he was unsteady on his feet," he said in evidence.
"His speech was slurred and he was repetitive."
It was difficult to get through to Kelly, the sergeant said.
"He refused to take part in the procedure. He was obstructive and difficult ... he was just stirring to muddy things up ... He was far too intoxicated to release and was held in custody until he sobered up."
After an adjournment, Judge Bergseng found police had proven the charge and convicted Kelly. The judge remanded him on bail for a pre-sentence report and sentencing on April 28.
