Lindsay Clancy did not have acute psychosis when she killed her three children but rather took their lives so they wouldn't "suffer" after she took her own life, a forensic psychologist testified Monday in her murder trial.

Kirk Heilbrun said he ruled out acute psychosis with command hallucinations because he didn't believe Clancy when she said she heard a voice telling her to "kill the children so you can kill yourself." "The way she described this as happening is that she heard a voice that she'd never heard before, experienced a hallucination and she's never experienced it since. But she only experienced it for the 18 minutes or so that it took to kill the children," Heilbrun testified.

"To put it mildly, that would be a very, very unusual pattern or manifestation of how this kind of thing comes about. Very unusual." A key issue at trial is Clancy's mental health.