This report, one in a series of occasional articles about oversight of nurses, was prepared in collaboration with ProPublica, an independent investigative newsroom in New York.

Tracy Weber and Charles Ornstein, both former Los Angeles Times staff writers, did significant reporting for this article before leaving The Times last year and have continued to cover the issue for ProPublica.

Maloy Moore, a Times researcher, and Doug Smith, The Times’ director of database reporting, contributed to this report.