Franklin Pierce was the 14th president of the United States, and he was arrested while serving as president for running down an old woman while on horseback. Pierce was never convicted of a crime connected to the incident, due to what the courts described as insufficient evidence. Though this incident is merely a historical blip, Pierce is reported to have a shaky safety record with horses in other areas, including an incident during the Mexican-American War in which he was pinned down by his horse, which was a major embarrassment for Pierce.
A newspaper story from 1927 that reports on the incident in which Pierce ran over a woman with his horse notes that the president was likely drunk at the time of the accident. This accident is said to have taken place in 1853, and any potential legal charges stalled out the same year. President Pierce was known to have a drinking problem throughout his adult life, and in fact his struggles with alcohol brought about the cirrhosis of the liver that ended up killing him. Political opponents made a mockery of both Pierce's alcoholism and his perceived cowardice as a result of his accident during the Mexican-American war.