A former police officer in Mexico, suspected of cutting off the ears or fingers of his kidnap victims to secure ransom money for their release, has been sentenced to life imprisonment.

The man, Daniel Arizmendi, was convicted of the kidnap and murder of a United States national.

It's the first of seven cases being brought against Arizmendi, who was arrested last year.

His wife, a former nurse, is said to have surgically removed the ears and fingers of hostages and posted them to relatives with a ransom note.