OTTAWA - Stephen Harper's lawyer says the former prime minister played no role in the decision by the RCMP and Crown attorneys to charge and prosecute Sen. Mike Duffy.

In an op-ed written for Postmedia newspapers, Robert Staley says it's impossible to believe Harper's interests were well-served by a raft of criminal charges that culminated in a politically charged, high-profile trial in an election year.

Ontario Court Justice Charles Vaillancourt acquitted Duffy of all 31 fraud, breach of trust and bribery charges last week, saying the Crown failed to prove its case beyond a reasonable doubt.

Staley says he didn't expect the Crown to win a conviction on the bribery charge, which stems from a controversial $90,000 payment on Duffy's behalf from Harper's former chief of staff Nigel Wright.

He also says the former Conservative leader never asserted that Duffy had been engaged in criminal wrongdoing -- only that his spending habits were politically unacceptable.

The Conservatives fell to official Opposition status in the October election after almost a decade in power, with Harper stepping down as leader but not as an MP.