The Los Angeles County Sheriff's Department will retest more than 4,000 DNA samples after announcing it used a faulty testing kit for at least eight months.

The Los Angeles County Sheriff’s Department says it will retest 4,000 DNA samples and open an internal investigation after learning that it used potentially flawed test kits for eight months.

The L.A. County Sheriff's Department used DNA testing kits for months without realizing they were faulty. An internal investigation has been launched.