An Iowa woman who is facing two counts of attempted murder in December hit-and-run attacks on two children — including one that the police said targeted a girl because she looked “Mexican” — has been ruled mentally incompetent to stand trial.

The woman, Nicole Marie Poole Franklin, 42, was declared unfit by a Polk County judge on Tuesday, according to court filings.

Ms. Franklin was also charged with a hate crime in a separate episode that the authorities said took place in between the Dec. 9 hit-and-run attacks. They said Ms. Franklin yelled racial epithets at a convenience store clerk and a customer in West Des Moines.

Law enforcement officials have characterized all three attacks as racially motivated. The victim of the first hit-and-run was a 12-year-old black boy, the authorities said.