Action News broke the story of the investigation last year, and we told you about the district attorney's decision not to pursue murder or manslaughter charges.
A judge was set to give Dr. Allen Clare probation in September until he learned new details about the case.
Clare will never be legally considered a criminal killer for his son's death. The mentally challenged 35-year-old named Patrick died in his father's dentist chair in April 2011.
Action News acquired a search warrant showing the dentist had injected valium and morphine into his son, and a coroner's report shows those narcotics killed the younger Clare. But prosecutors initially charged his father with just a business code violation and Clare pleaded "no contest", expecting to be sentenced to probation.
"The district attorney's office here is tough on crime," said Clare's defense attorney, Mark Broughton. "They prosecute cases to the fullest. They, as well as I, have viewed this case, have viewed all the evidence in the case that we have so far -- much of which you don't yet have -- to be able to assess this case and that's why we resolved it where it was to begin with."
The 68-year-old had already given up his dental license and cleared out his office to meet terms of the plea deal. But he left court in September potentially facing more serious charges after Judge Jon Kapetan busted the plea deal.
"It was shock and disappointment, dismay," said Broughton.
Coalinga police say when they drilled down into the case, they found evidence supporting at least a manslaughter charge. First off, Dr. Clare wasn't allowed to use valium or morphine.
"These are medicines that he was not licensed to prescribe, so therefore it was illegal for him to possess and dispense these," said Coalinga police chief Cal Minor.
A California Dental Board complaint accused Dr. Clare of illegally using valium 34 times. But he only used morphine once -- on his son -- and police say he ordered the drug months in advance.
Prosecutors reviewed the case and decided against filing new charges against Clare. But Judge Kapetan said he believed the case needed to move forward to a preliminary hearing where prosecutors would have to present evidence. That's now scheduled to happen in November.