Jury selection is set to begin Wednesday for one of three defendants charged with murdering their mothers in San Luis Obispo County.

While the three cases are unrelated, all three defendants allegedly had mental health issues.

Christopher John Shumey, 36, of San Luis Obispo, is the first of the three to go to trial. Previously diagnosed with bipolar disorder, Shumey had been to Santa Barbara Cottage Hospital, feeling suicidal, roughly 10 days before he allegedly shot his mother, Karen Shumey, 65, in September 2011. While he and his mother had met for dinner and a movie the day before she was killed, Shumey allegedly became angry at her for showing up unannounced the following day.

Shumey also allegedly fired on law enforcement officers who arrived on the scene shortly after Karen Shumey was shot.

Michael Van Heuver, 24, of Los Osos, another defendant charged with murdering his mother, appeared in court Tuesday, when his trial — originally set to begin next week — was pushed back to Feb. 26. Last May, he was charged with murder after his mother, 56-year-old Lisa Ann Van Heuver, was taken off life support. Van Heuver allegedly assaulted her.

In both cases, relatives said the mothers were trying to help their sons with mental health issues. Van Heuver also allegedly had substance abuse issues.

A third defendant accused of killing her mother, Sunni Daun Jackson, 36, of Paso Robles, is currently deemed incompetent to stand trial due to mental health concerns. Jackson, diagnosed with schizophrenia, allegedly stabbed and beat 61-year-old Earlene Louis Grove to death in April 2012.

Her case is suspended indefinitely until she is able to assist in her defense.