A Colorado father and mother who had reported their six-year-old son had been carried away in a helium balloon last month will plead guilty in the case, a lawyer for the boy's father says.The helium balloon constructed by the Heene family travelled more than 80 kilometres after it broke free of its tethers last month. (KMGH-TV/Associated Press)

Richard Heene will plead guilty to attempting to influence a public servant, a felony, while his wife, Mayumi, will plead guilty to false reporting to authorities, a misdemeanour, David Lane said in a statement.

The Heenes have agreed to turn themselves in and are scheduled to appear in court on Friday, according to the district attorney's office.

The charge against Richard Heene carries a possible sentence of two to six years in state prison and a fine of up to $500,000, prosecutors said. Mayumi Heene could face up to six months in county jail and a fine up to $750.

Lane said he expects prosecutors to ask for jail time for both parents. But because of the deal, the maximum jail time would be 90 days for Richard Heene and 60 days for his wife.

The most serious of the charges recommended by Larimer County Sheriff Jim Alderden would have carried a maximum sentence of six years in prison.

Lane said prosecutors insisted on a package deal that required Richard Heene to plead guilty to a felony so Mayumi Heene could plead guilty to a misdemeanour. He said Mayumi was basically threatened with deportation unless there was an agreement on the deal.

All a hoax

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

Richard and Mayumi Heene 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.Six-year-old Falcon Heene sits in the box of his family's pickup truck outside the family home in Fort Collins, Colo. His parents are pleading guilty to charges related to the incident. (David Zalubowski/Associated Press)

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.

But 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 is 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 they may 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