Retired Portland detective sergeant Bruce Robert Coffin makes the most of his professional expertise in his third Maine-based crime novel, “Beyond the Truth.”

When veteran cop Sean Haggerty responds to an armed robbery at the Bubble Up Laundromat, the call does not seem particularly unusual for Portland on a Saturday night. But once he starts pursuing the suspects, things quickly spin out of control. Haggerty damages his cruiser, sets off on foot and ends up confronting one of the hoodie-and-ski-mask-wearing robbers in a dark alley. Within an instant, a popular high school athlete is shot to death.

Detective Sargent John Byron and his Criminal Investigation Division team arrive on the scene and are disturbed when no gun is found, only a phone whose flashlight mode may have spooked Haggerty. With the second suspect on the loose, public opinion turns against the officer. Soon there are public protests and political grandstanding by the mayor and the acting chief of police.

Dedicated to uncovering the truth, Byron also wants to protect his friend and fellow officer, and he uses his interrogation skills to push back against those who would condemn Haggerty without examining the facts. What Byron doesn’t know is that someone has ordered a hit on Haggerty, and that contract killer is drawing ever closer.

Shootings by the police of unarmed suspects are rightfully a cause for deep concern, and “Beyond the Truth” treats the issue with respect, acknowledging that not all such shootings are justified. Byron has his theories about what happened, but he doesn’t assume he can prove them. Coffin writes, “Byron knew that finding and bringing to justice those responsible was all he could ever offer in these cases, but it came with no guarantees. Justice, even when served, never soothed the ache, never brought back a son or daughter.”

Coffin began the John Byron series with 2016’s “Among the Shadows” and continued it in “Beneath the Depths,” in 2017. Byron may remind some mystery fans of Michael Connelly’s Harry Bosch or Lawrence Block’s Matthew Scudder. He’s got a smart mouth that gets him in trouble, he doesn’t always play by the rules, and he turns to alcohol when he’s feeling at his lowest. He is, nevertheless, a unique creation, set apart from some better-known fictional investigators by his Maine background, his acerbic Down East wit and the family tragedy that still haunts him from this youth.

The supporting cast of “Beyond the Truth” is well defined, from eager-to-please computer expert Dustin Tran to Byron’s boss, Lieutenant Martin LeRoyer, who might not be as bad a guy as some people think, to the multi-ethnic suspects from the local high school. Byron has a love interest in Diane Joyner, the police department’s press liaison, and their developing relationship gives “Beyond the Truth” an extra dose of urgency when things go wrong.

Coffin sometimes allows his prose to drift into cliche – “Sean Haggerty was a cop’s cop. In his early thirties and built like a linebacker, he was a gentle giant.” Coffin’s style works best when it’s allowed to flow naturally, especially when describing how cops perceive the streets they patrol: “The snow piled against the apartment building walls seemed to dance in the flickering blue light of his cruiser’s strobes, making the alley look like a disco.”

From the beginning of the series, Byron has struggled with alcohol addiction. In “Beyond the Truth,” Haggerty’s predicament – as well as a personal loss that comes from out of nowhere – sends the detective into a tailspin of booze and bad behavior. It’s to Coffin’s credit that the scenes of Byron’s fall don’t feel melodramatic but are grounded in their presentation of one complicated man’s ongoing battle with trauma in both his family and his job.

Always engaging, “Beyond the Truth” has the feeling of the veracity when it comes to describing the details of a criminal investigation and the day-to-day realities of life as a police officer. The final scenes bring Byron to a pivotal point in his career and his private life. Fans of well-observed crime fiction will be rooting for him to make the right choice.

Berkeley writer Michael Berry is a Portsmouth, New Hampshire, native who has contributed to Salon, the San Francisco Chronicle, New Hampshire Magazine, the Los Angeles Review of Books and many other publications. He can be contacted at:

mikeberry@mindspring.com

Twitter: mlberry