Cry Wolf by Kathi Oram Peterson

Dyani Blackwolf is bursting with excitement: after years of disappointment, she’s just learned she and her husband are one step closer to having their dreams come true. Eager to tell her husband, Matthew, about her findings, she returns home from her nightshift at the hospital—but what awaits her there is no dream. It’s a nightmare. Matthew has been murdered, and Dyani is the only witness to the masked intruder. With no one to corroborate her story, she is the prime suspect.
When U.S. Marshal Brett Rollins’s best friend, Matthew, was murdered, Dyani, was convicted of the crime. But it’s never added up for Brett. Now, three years later when Dyani escapes prison and Brett finds her, he is faced with a life-altering choice: send a woman he believes to be innocent back to prison or help her find his friend’s killer. Determined to see justice done, Brett goes rogue. The unlikely allies embark on a dangerous quest to uncover the truth. But what they discover is a plot more far-reaching than they ever imagined and a truth that will test everything they thought they knew.