The Colorado parents who falsely reported that their six-year-old son had been carried away in a helium balloon last month pleaded guilty to charges on Friday that could see them get jail time and probation.

Richard Heene, father of the so-called balloon boy, pleaded guilty in district court in Fort Collins, Colo., to attempting to influence a public servant.

His wife, Mayumi, pleaded guilty to the misdemeanour of false reporting to authorities, said the family's lawyer, David Lane.

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Richard Heene, centre, follows his son, Falcon, as his wife, Mayumi, locks the door as they leave their home in Fort Collins, Colo. The Heenes pleaded guilty Friday to influencing a public servant and false reporting to authorities.

Lane said Mayumi Heene, a Japanese citizen, faced deportation should she be convicted of more serious charges.

The prosecution agreed to let her plead to the misdemeanour charge as long as her husband pleaded guilty to a felony.

The Heenes agreed to turn themselves in earlier this week.

Attempting to influence a public servant is a felony that carries a possible sentence of two to six years in state prison, plus three years on mandatory parole, and a fine of up to $500,000, the judge explained to Heene in court Friday morning.

But Lane said that because of the plea agreement, he expected the maximum jail time to be 90 days for Richard Heene and 60 days for his wife.

Husband initially denied stunt was a hoax

Last month, police concluded the balloon incident, which started a media frenzy, was a hoax.

The Heenes had told authorities they were certain that Falcon, the youngest of their three children, had crawled inside the helium balloon — built in their yard as a science experiment — before it floated away on Oct. 15.

Television cameras followed the balloon for 80 kilometres before it landed; a search then showed no one inside. A few hours later, Falcon was found safe at home, hiding in the rafters of his family's garage.

Questions about the veracity of the story were raised after the family was interviewed by CNN's Wolf Blitzer on the Larry King Live show. During questioning, Falcon was heard telling his father that he didn't come out of the attic when called because they were "doing this for the show."

The Heene family has been featured twice on the ABC television reality show Wife Swap — the last time in March — fuelling speculation that they might have been seeking more publicity.

On Oct. 17, deputies questioned both parents separately. Richard Heene denied the incident was a publicity stunt, but Mayumi Heene admitted it was a hoax, according to a search warrant affidavit.

She told an investigator the couple devised the hoax two weeks before the flight "to make the Heene family more marketable for future media interest" and that they built the balloon specifically for that purpose. Mayumi also said she and her husband had instructed their three children to lie to authorities and the media, the affidavit said.

With files from The Associated Press