A US doctor has been found guilty of waterboarding his stepdaughter by holding the child's head under a tap.

Melvin Morse, 60, was convicted of one felony, waterboarding in the bathtub, and five misdemeanours.

Morse, who has appeared on The Oprah Winfrey Show and Larry King Live to discuss his work, has researched near-death experiences involving children, but he denied police claims that he may have been experimenting on the girl.

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Defence lawyers argued “waterboarding” was a term jokingly used to describe hair washing that the girl did not like.

Morse was charged with endangerment and assault after the girl ran away in 2012 and told authorities of waterboarding and other abuse.

He could face several years in prison when he is sentenced on 11 April.

Morse, whose medical license was suspended after his arrest, has written several books and articles on paranormal science and near-death experiences involving children.

The girl's mother, Pauline Morse, 41, pleaded guilty last year to misdemeanour endangerment charges and testified against Melvin Morse.

Pauline Morse and her daughter, now 12, testified that Melvin Morse used waterboarding as a threat or a form of punishment. Waterboarding as used in the past by US interrogators on terror suspects simulates drowning. Many critics call it torture.

According to testimony, the allegations of waterboarding surfaced after the girl ran away.

The girl went to a classmate's home the morning after Morse grabbed her by the ankle and dragged her across a gravel driveway into the home, where she was spanked and warned of worse punishment the next day. When investigators questioned the girl, then 11, she told them about what she called waterboarding.

Prosecutors argued that in addition to being waterboarded, Morse subjected the girl to other abuse, including being forced to stand with arms outstretched for hours at a time; being confined to her room, where she had to use her toy box or closet as a toilet; and being deprived of food or force fed until she vomited.

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Prosecutor Melanie Withers portrayed Melvin Morse as a brutal and domineering “lord and master” of his household, abusing the girl for years while her mother acquiesced in silence.

Pauline Morse said she chose to ignore the abuse, saying she was afraid of “undermining” Melvin Morse. She also testified that she did not have a close relationship with the girl for several years that encompassed the waterboarding, and that she did not pay her much attention.

The girl and her younger sister remain in foster care but are allowed supervised visits with Pauline Morse. Pauline Morse said she hoped her cooperation with prosecutors will bolster her chances of being reunited with her daughters.

AP