Prince Elias McLeod Rams (Family photo)

Virginia’s chief medical examiner has reversed a ruling that a 15-month-old boy died by drowning in Manassas in 2012, finding that the cause of Prince McLeod Rams’s death “should be changed to undetermined” and that “the possibility of a natural death cannot be totally eliminated.”

The reversal was one of two key setbacks Friday for Prince William County prosecutors, who are seeking the death penalty against the boy’s father, Joaquin S. Rams, whom they suspect of killing his son and two others as part of an attempt to collect six-figure insurance payouts. Prosecutors moved to use the other two uncharged slayings as evidence against Rams, but Prince William Circuit Court Judge Craig D. Johnston denied their request. The judge ruled that “a propensity” to commit crimes is not admissible to prove guilt in one specific case.

“The case against Mr. Rams is incredibly weak” after the medical examiner’s reversal, defense attorney Tracey Lenox said, arguing that prosecutors were trying to save the case by introducing two uncharged slayings. And the judge prohibited it, saying it would lead to “three murder trials in one.”

Rams, 42, has been in jail without bond since his arrest in January 2013. Police in Manassas, where Prince Rams was allegedly slain in October 2012, long suspected Joaquin Rams in the March 2003 shooting death of his ex-girlfriend, Shawn Mason, and the November 2008 asphyxiation of his mother, Alma Collins, which was ruled a suicide.

In June 2013, prosecutors convened a special grand jury to hear evidence about the three cases. That grand jury then increased the murder charge in the Prince Rams case to capital murder and handed up a murder indictment for the slaying of Mason.

Joaquin Shadow Rams (AP)

But last August, prosecutors quietly dismissed the murder charge in the Mason case. Assistant Commonwealth’s Attorney James A. Willett was not available to comment after Friday afternoon’s hearing. No trial date has been set in the death-penalty case.

In addition to the sudden deaths of three people close to Joaquin Rams, all three had significant life insurance policies, including three policies totaling more than $500,000 on his young son, raising investigators’ suspicions. Prosecutors said that Rams inherited more than $162,000 from his mother’s estate but has not received any money from the policies for his son and ex-girlfriend.

“It is really the money that binds these cases together,” Willett told the judge, “and establishes a single criminal enterprise.”

But the prosecutor said he also needed the evidence of the other two deaths because “we don’t have any direct evidence of the manner of death, as a result of” the new report by William T. Gormley, the state’s chief medical examiner. Instead, Willett said, the other cases would provide circumstantial evidence that Rams killed his son.

The new medical examiner’s report was sent to prosecutors last week. It overrules the original autopsy done by Constance R. DiAngelo, an assistant chief medical examiner for Northern Virginia, who concluded that because Prince was found naked, wet and cold and had fluid in his sinuses, lungs and intestines, he must have drowned.

Rams’s attorneys argued last year that the boy was wet because his father had found him having a seizure, took him to a bathtub and splashed cold water on him until paramedics arrived. They also noted that Prince was on life support for more than a day, receiving intravenous fluids, before he died at Inova Fairfax Hospital on Oct. 21, 2012. The boy also had previously suffered a series of febrile seizures, or convulsions, including four in 24 hours the month before he died.

So Gormley reviewed DiAngelo’s autopsy and in a letter to Prince William prosecutors wrote, “I have determined that the cause of death should be changed to undetermined.” He said the fluid in Prince’s body could have been caused by the fluids received in the hospital and that “some form of generalized epilepsy associated with febrile seizures cannot be ruled out and is supported by the history. . . . A homicidal manner of death cannot be proven to a reasonable degree of medical certainty with the available data.”

Gormley was not available Friday to explain why he revisited the case, his assistant said.

But court records show that prosecutors were already searching for second opinions on the cause of death and did so shortly after a series of articles in The Washington Post last year in which medical experts and Rams’s attorneys questioned the drowning finding. Assistant Commonwealth’s Attorney Teresa A. Polinske contacted a forensic pathologist in Kentucky, a pediatric neurologist and epilepsy expert in New York, and a pediatric emergency doctor in Richmond. The prosecutor sent medical and police records, photos and surveillance videos and the articles in The Post.

Court records show that the emergency doctor agreed with the determination of a drowning. The neurologist concluded that Prince had been asphyxiated or drowned. The forensic pathologist strongly disagreed with the drowning finding, saying the death was possibly seizure-related and consistent with “Sudden Unexplained Death in Childhood.”