A Christchurch woman is warning people to be careful of who they let into their homes after her flatmate caused her "a year from hell".

Janice Kerr, 40, said Kim Winitana moved into her rented Sydenham house after the February 2011 earthquake.

The pair had not known each other before that, but at first Winitana, 39, seemed "fine" and often helped out around the house.

In January this year, Winitana started "acting weird", Kerr said.

He began by asking if he could sleep with her, to which she said no. He apologised the next day, but started to "get a bit obsessed" during the next few months.

During one incident, he allegedly walked into the lounge wearing only a T-shirt.

In another, Kerr said, she found he had been in her bed and was watching her get changed in her bedroom.

She yelled at him, but he "barged in" to her room.

The next day she found he had been in her bed again, prompting her to call the police.

After his stint living with Kerr, Winitana was convicted of burglary, theft, performing an indecent act with intent to insult and driving while prohibited. He will be sentenced on November 27.

The theft charge related to three rings stolen from Kerr's house while he was living there.

"He sat here and sympathised with me. I was throwing up because I was so flipping upset," Kerr said.

One was her grandmother's engagement ring, and the others belonged to her mother.

The rings were worth more than $1500 each, but were priceless to Kerr because of their sentimental value.

Kerr said Winitana had made the past year "a year from hell".

Her new flatmate was someone she knew well, but she advised anyone considering getting a flatmate to make sure they received credible references.

A police spokesman said landlords and tenants were not able to check a person's criminal history through the police vetting process.

Citizens Advice Bureau service manager Mollie Howarth said residents should screen a new flatmate carefully before letting them move in.

"It's human nature that we don't look into stuff enough," she said. "You think it'll be all right, but you can get yourself into a whole world of hurt."

She advised anyone getting a flatmate to make sure both parties signed a house-sharing agreement and to spend time with each other before the flatmate moved in.

"At a bare minimum, you actually need to be checking out the references of people because they're going to be sharing that intimate space with you," she said.

"You want to be selective and using your discretion."

- © Fairfax NZ News