Teri Sopp is a Senior Examiner in the SID unit of LAPD. Her job involves matching crime scene fingerprints to individuals. In September 2009 Harry Bosch brought her a 9 mm shell casing for examination. The casing had come from the autopsy of John Li. She said that ordinary methods could not reveal a print on a shell that had been fired because the high heat evaporates all oils that might have been left. However, a new technique called electrostatic enhancement was showing promise for revealing prints under the right conditions. She told Bosch that she would have to get authorization before using the new technique.
On 15 September 2009, she called Bosch to tell him that she had received authorization and she had found a print on the casing. The print was matched to Henry Lau, and she gave him Lau's address. This was the turning point in the investigation of Li's murder.