At first, comedian Jim Carrey seemed an odd choice for the romantic lead in a gay prison love story. Just a decade ago, he was earning millions a pop to lend his zany antics to sophomoric box office hits like The Mask, Ace Ventura, Pet Detective, Liar Liar and Bruce Almighty. But, like many character actors, his signature style eventually became tiring, even monotonous, and he fell from favor as film offers starting drying up.

Would he be able to tone it down enough to convincingly play a flamboyantly gay man? Fortunately, I Love You Phillip Morris, the screen adaptation of an “improbable but true story” of a gay con man, provides just the vehicle for Carrey to mature as an actor.

Based on a book by former Houston Chronicle investigative reporter Steve McVicker, I Love You, Phillip Morris tells the story of notorious real-life convict Steven Russell, who is serving a 144-year sentence in Texas.

Directors John Requa and Glenn Ficarra infuse the tale with wry, dry humor as we follow Russell through tumultuous events in his life — discovering that he was adopted; his hum-drum, model life as a father, police deputy and church organist; the rejection by his birth mother — all seemingly told from Russell’s death bed.

After a serious automobile accident, Russell makes a life-changing decision to accept his homosexuality, leave his family and take up residence with a hot Latino boy toy (Rodrigo Santoro) in South Beach. He leads the glitzy high life by committing insurance fraud and credit card schemes, until the law catches up.

During his first stint in prison, he meets the titular character, Phillip Morris (Ewan McGregor), and immediately becomes smitten. He puts his skills to work to secure their eventual release, going so far to impersonate Morris’ attorney in court.

Theirs is a conventional gay romance — don’t expect any prison action a la Oz — and they set up a fabulous home (complete with matching his-and-his convertibles) after Russell works his way into a corner office with a health-care billing corporation and immediately begins embezzling funds.

As expected, Russell winds up in prison again, where he engineers his ultimate scam in an effort to escape and win back Morris. Without spoiling the twist, let’s just say he successfully cheats death.

I Love You, Phillip Morris is not an action pic and at times it is blatantly predictable, at least until Russell’s next unbelievable scheme hatches. And there is little romantic chemistry between Carrey and McGregor, although the Scotsman is charming as the naïve Southern boy who finds tender love in the most unlikely place. But the film is most successful as a farcical commentary, questioning the blind justice of the law, societal conventions of love and marriage, the excesses of ’90s gay culture and even AIDS, all issues raised by the likeable sociopath Russell.