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 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.

"We take the integrity of our criminal investigations and the reliability of our forensic testing very seriously,” L.A. County Sheriff Robert Luna said.