WASHINGTON — A retrial in the 2015 murder of a 21-year-old transgender woman, allegedly by a longtime friend, begins Monday.

Montgomery County prosecutors say Rico LeBlond, who is now 22, shot Zella Ziona in an alley behind a Gaithersburg, Maryland, shopping center, in October 2015.

A jury deliberated for three days, but was unable to reach a unanimous verdict, in January 2017. Montgomery County Circuit Court Judge Anne Albright declared a mistrial.

Prosecutors have said that LeBlond was embarrassed when Ziona, a transgender woman, flirted with him in front of his male friends. Ziona had transitioned from male to female in the months before she was murdered.

LeBlond had known Ziona since middle school, according to prosecutors. Ziona was born DeAndre Smith.

In LeBlond’s first trial, defense attorney David Felsen said several witnesses had provided conflicting descriptions of how Ziona had died.

If convicted, LeBlond could face life in prison.