YAKIMA, Wash. — A man accused of helping Kevin Harper dispose of property stolen in a 2011 West Valley triple homicide has reached a plea deal with prosecutors.

Tennance Buckingham, 50, is expected to plead guilty today in Yakima County Superior Court to charges of first-degree rendering criminal assistance and first-degree trafficking in stolen property, prosecutors said.

Chief Criminal Deputy Prosecutor Ken Ramm declined to describe the deal, which could have implications on the stalled case against Harper, once the prime suspect in the slayings.

Ramm did say Buckingham is not expected to be taken into custody as a result of the plea deal. The defendant is currently free on bail.

Buckingham was one of four people who once faced charges in the February 2011 bludgeoning deaths of Bill Goggin, owner of a Yakima civil engineering firm, his wife, Pauline, and his mother, Bettye.

Their bodies were found in the family’s home in the gated Falcon Ridge development, west of Yakima. Authorities believe they were killed during a burglary.

Harper, who turned 31 in jail Tuesday, was considered the prime suspect until prosecutors were forced to cut a deal with him following a series of missteps by investigators and prosecutors that threatened to derail the case.

Harper subsequently pleaded guilty to two relatively minor charges — first-degree unlawful possession of a firearm and second-degree possession of stolen property — related to the theft of a Western-style, .22-caliber pistol from the Goggin home.

In exchange for his plea, prosecutors agreed to recommend a prison sentence of just over seven years. They also dismissed accessory charges against his wife, Crystal Gray-West.

Murder charges against Harper have not yet been officially dismissed. Under the plea agreement, the murder charges were to be dropped when he is sentenced on the possession and theft charges. However, the case was turned on its head last month when prosecutors accused him of violating the terms of a secret “confidential agreement” with the prosecution.

In response to a request by prosecutors to hold a closed-door hearing for the purpose of nullifying the plea deal, trial judge Ruth Reukauf instead scheduled a hearing June 13 to hash out the merits of the request.

Harper’s attorney, meanwhile, accused prosecutors of cutting the deal in bad faith to buy time for investigators to further investigate his client.

Buckingham has a lengthy criminal record in Alaska and Washington that includes convictions for residential burglary, theft, drugs and weapons offenses.

In previous filings in the case, sheriff’s detectives suggested that Buckingham was helping Harper dispose of evidence from the homicide scene.

Harper mentioned Buckingham’s name during a police interview, and investigators tracked down another man who said he had bought a laptop computer from Buckingham that was one of two believed to have been taken from the Goggin home.

Accessory charges against a fourth defendant, Tracy Culton, were dismissed in February after prosecutors said further investigation found insufficient evidence to proceed against her.

• Chris Bristol can be reached at 509-577-7748 or cbristol@yakimaherald.com. Follow him on Twitter at twitter.com/ChrisJBristol.