A niece of assassinated US president John F. Kennedy has been cleared of driving while under the influence of drugs.

Kerry Kennedy gave herself a round of applause after the verdict not guilty was read out in the New York county court, she faced up to a year in jail if convicted.

According to court reports the 54-year-old took a sleeping pill before setting off on an erratic five-mile drive in her luxury SUV in July 2012.

She argued that she took the tablet by accident, mistaking it for her morning thyroid medication.