Sawyer Robison was originally charged with the attempted murder of the two officers and second-degree murder in the death of his uncle, Bradford Clarke, after a standoff on the family farm near Killam in February 2012.
But Alberta Justice spokeswoman Michelle Davio said Friday the murder charge will be discontinued when a preliminary hearing resumes in court on Monday.
She said the prosecutor recently received evidence from the RCMP related to Clarke's death.
"Upon reviewing the evidence, the second-degree murder charge will be discontinued because there's no reasonable likelihood of conviction," Davio said.
She said she couldn't give details about the new evidence.
Davio added that it is possible to reactivate the charge if something more comes forward.
The lawyer who acted for Robison at previous court hearings, Brian Beresh, did not immediately return calls seeking comment.
Robison, 28, still faces two counts of attempted murder as well several weapons offences, including possession of a prohibited, loaded, restricted firearm and possession of a firearm with altered or defaced serial numbers.
The charges were laid after four officers went to execute a search warrant on the farm, about 160 kilometres southeast of Edmonton.
RCMP said at the time that shots were fired shortly after two of the officers walked into a house on the farm.
Constables Sheldon Shah and Sid Gaudette were hit but made it back outside.
Clarke was later found dead in the home and a manhunt began for his nephew.
Robison was arrested peacefully three days later on a rural road in the area after his parents made an emotional public plea asking him to turn himself in.
The wounded officers underwent surgery in hospital and were later released.
They returned to work last summer.