Joey Rovero, one of Tseng former patients, died nine days after his last visit to obtain prescription meds from Tseng.
"Had she done a thorough exam, she would have never prescribed the medications that she did. That's so obvious as I hear the testimony," said Rovero's mother, April.
Tseng is accused in the deaths of Rovero and two other young men and over prescribing drugs to many others. A medical board investigator testified that Tseng failed to do even basic exams before prescribing powerful painkillers to patient after patient.
Tseng faces 24 felony counts. Two of them involve her patient, Lana Rau, who testified she saw Tseng for nearly four years, sometimes as often as once a week to make her request for about 400 pills a week.
Rau also said when she requested more, the Rowland Heights doctor would do it by writing prescriptions to Rau's husband, even though he never went to Tseng's office.
However Tseng's defense is shifting the blame to Rau for demanding the drugs. During a cross-examination, she testified Friday that she was aware that she was abusing prescription pills.
Murder charges are rare for a doctor. But the prosecution alleges that in this case, Tseng was aware that she was endangering patients. She had settled five wrongful death suits in the past, all involving young people.
"She knew what she was doing and she was the professional and she should have said no," said Jodi Barber, whose son Jarrod overdosed after taking opana he received from a friend who was under Dr. Tseng's care.
The prosecution has called 26 witnesses so far and they expect to call at least 24 more. The case is about half way through for the prosecution.
If she is convicted on all counts, Tseng could face 45 years in prison.
CORRECTION: This story earlier reported that Jodi Barber's son, Jarrod, was a patient of Dr. Tseng's. Barber's son was never under Tseng's care.