The prosecutor who took the rare step of murder charges against a doctor Friday said the situation should serve as a warning to unscrupulous doctors becoming pill machines. Los Angeles County District Attorney Steve Cooley said his office will continue prosecuting greedy and unethical doctors after charging Hsiu-Ying Tseng, 42, with three counts of second-degree murder and 21 felony counts. If convicted of murdering Vu Nguyen, 29, of Lake Forest, on March 2, 2009, CPP film; Steven Pham, 25, of Palm Desert, on April 9, 2009; and Joseph Rovero III, 21, an Arizona State University student from San Ramon, on Dec. 18, Tseng could face life in prison. Of about 880,000 registered doctors prescribing nationwide, federal agents investigate between 200 and 300 dirty doctors suspected of wrongdoing annually, DEA spokesman Rusty Payne said. But bringing a murder charge against a doctor in a case where a patient dies of an overdose is extremely rare. "I am really strict, www.wangji.cc, I follow my patients, guidelines.. If my patient decides to take a month's supply in one day, then there is nothing I can do." In 2008, Harriston Bass was convicted of second-degree murder in the death of Gina Micali, 38, who died after taking hydrocodone painkillers in Nevada. Bass was sentenced to 25 years to life in prison. A Georgia doctor was convicted in October 2007 in the death by overdose of his patient and housemate. Noel Chua was found guilty of felony murder and violating the state's controlled substances act in the death of Jamie Carter III from ethanol poisoning. In receiving prescriptions for oxycodone and ketamine from Chua's meticulous records, Carter was also drunk. In Florida, Dr. Sergio Rodriguez faces three first-degree murder charges in deaths by overdose. "This case goes beyond anything else we've seen," he said, emphasizing that these types of cases must be carefully scrutinized before extreme murder charges are filed. Tseng made her first court appearance Friday wearing a pink shirt and looking despondent. She sobbed incessantly as proceedings were postponed until March 9, when her bail, currently set at $3 million, will also be reconsidered, wrought iron manufacturers. Her attorney declined to comment after the hearing. Tseng, a licensed osteopath, and her husband, also a doctor, opened a storefront office in the Los Angeles suburb of Rowland Heights in 2005. Three years later, she was under investigation by the Drug Enforcement Administration and the California Medical Board for writing questionable prescriptions reported by pharmacies. The patient deaths were connected to her in 2009, according to officials, but not all led to murder charges. Tseng wrote more than 27,000 prescriptions in the three-year period beginning Jan. 25, 2007 - an average of one per day, according to a DEA affidavit. DEA agents swept her office in 2010 suspending her license to prescribe and her medical license. She voluntarily surrendered her osteopathic medicine license this week to the California Medical Board. Her husband continues to run their clinic. This case highlights a particularly dark area because these patients addicted to prescribed medications seek out a source for their habit. Prosecutors have charged numerous doctors and pharmacists with illegally dispensing prescription drugs, arguing they wrote prescriptions outside the usual course of professional practice and not for legitimate medical purposes. Related thematic articles: Children's behavior linked to snoring Fans dream way to most popular Apple computers Doctor accused of killing patients by overdosing on three prescriptions Fans dream way to most popular Apple computers Children's behavior linked to snoring