A TASMANIAN man set up a video camera to capture paranormal activity instead filmed his partner engaging in a sexual relationship with his teenage son, a court has heard.

The 28-year-old woman pleaded guilty to five counts of having sexual intercourse with a minor in Tasmania's Supreme Court, The Mercury reports.

Crown Prosecutor Jackie Hartnett told the court in October last year the woman had gone to the boy's room to discuss his driving lessons, but this had eventually led to intercourse.

The following day, the woman's de facto partner set up a video camera in an effort to capture evidence of paranormal activity in the house, but had forgotten to turn it off.

When he returned reviewed the footage, he saw his son and the woman kissing and cuddling. She downplayed the incident when he quizzed her about it, but his son confessed that they had sex three times.

The man called the police and the woman admitted during a video recorded interview to having sex with the boy twice and admitted knowing he was sixteen. She was ashamed and embarrassed by her conduct, but mistakenly thought 16 was the age of consent.

Ms Hartnett told the court that in the following weeks the woman followed the boy to another part of the state where they had sex several times in a hotel room.

She has been remanded in custody and is due to be sentenced on Monday.

Read more about this case at The Mercury's website.