WHITE PLAINS, N.Y. -- A New York state trooper testified Tuesday at Kerry Kennedy's drugged-driving trial that he was concerned she may have suffered a seizure or stroke after her car swerved into a truck in 2012.

Trooper Bradley Molloy said Kennedy passed several drug tests that he administered at the police station. The tests included having Kennedy follow the tip of a pen with her eyes, stand on one leg and touch the tip of her finger to her nose, Molloy said.

Kennedy told the trooper that she had consumed some carrots and a cappuccino that morning and had slept about eight hours the night before. Molloy said Kennedy also told him she was concerned that she might have accidentally taken a sleeping pill instead of her thyroid medication, which were next to each other on her medicine cabinet.

"The defendant was not impaired by any drug," Molloy said. "I feel she may have suffered a medical condition while driving."

Molloy said Kennedy was polite and co-operative.

On Monday, a North Castle town police officer, Joel Thomas, said he had administered four field sobriety tests, involving eye movements, walking and turning, reciting part of the alphabet and standing on one leg. Kennedy only passed one, reciting the alphabet from J to T, he said.

Kennedy is the ex-wife of New York Gov. Andrew Cuomo, daughter of Sen. Robert F. Kennedy and niece of President John F. Kennedy. Her mother, Ethel Kennedy, and a sister, Rory Kennedy, were both in the courtroom.

On Monday, motorists testified that Kennedy swerved her Lexus into a truck, damaging the car and blowing a tire, but kept driving and later was slumped at her steering wheel and disoriented.

In his opening statement, defence lawyer Gerald Lefcourt said Kennedy was not disputing that she drove erratically. But he said it happened because Kennedy accidentally took an Ambien sleeping pill that morning instead of her thyroid medication.

Prosecutor Stefanie DeNise said even if the pill were taken accidentally, Kennedy violated the law "by failing to stop and pull over as she felt the onset of symptoms."