The unusual circumstance of a judge also serving as the jury enabled the judge in the Joaquin Rams murder trial to again cross-examine a defense witness for more than a half-hour Wednesday, eventually poking a crucial hole in Rams’s claim that his 15-month-old son suffered a fatal seizure rather than being drowned, while the defense team sat in silent distress.

Prosecutors in Prince William County, Va., have been claiming for four years that Rams, 44, drowned his toddler Prince McLeod Rams in October 2012. But Circuit Court Judge Randy I. Bellows seems to be exploring an alternate theory of the case: that Rams suffocated the boy, placed him in a crib next to his teenage son, then rushed in and claimed he splashed water on Prince because he was “really hot,” according to the 911 tape. Bellows has focused on the fact that when paramedics arrived, they found Prince cold to the touch and with no heartbeat. The boy’s heartbeat was not restored for more than a half-hour, and after more than a day on life support, he died.

The assistant medical examiner who performed the autopsy on Prince ruled he was drowned, and Rams was charged with murder in January 2013. The medical examiner, Constance DiAngelo, based her ruling in part on the fact that paramedics reported Prince cold to the touch, discounting the father’s claim that Prince had been having a febrile, or fever-induced, seizure. In 2014, DiAngelo’s boss, Chief Medical Examiner William Gormley, changed the cause of death to “undetermined,” and both he and other defense experts testified that fluid in Prince’s body could have resulted from the aggressive attempts to save the boy.

So when the defense on Wednesday put Brian Bridges on the witness stand, they wanted to use his experience as a pediatric intensive care doctor at Vanderbilt University Children’s Hospital to explain how a seemingly harmless febrile seizure could lead to hypoxia, or lack of oxygen, which in turn could cause a heart attack that would shut down the toddler’s body. Prince had suffered six febrile seizures in the six weeks before his death, including one which Bridges said was 15 to 20 minutes in duration. The defense showed a photo of Prince’s crib sheet with a pink stain on it, which Bridges said may have been a mix of blood and fluids coughed up during cardiac arrest.

Bellows asked if someone in cardiac arrest would be moving. “A patient in cardiac arrest would have no movements,” Bridges said.

Bellows then returned to the 911 call placed by Rams’s housemate, Roger Jestice, with Rams shouting in the background. “Rams says, ‘He’s shaking, but he’s not breathing,’ ” Bellows recounted, of a tape he said he had listened to 20 times. “If he [Prince] is shaking then, is that consistent with him being in cardiac arrest in the crib a period of time earlier?”

“No,” Bridges said.

Bellows returned to the paramedics’ observation that Prince was cold to the touch when they arrived. “If the child’s heart had stopped beating,” Bellows asked, “how quickly could he have gone cold to the touch, and had a febrile seizure?” Bridges said he didn’t know but noted that of the children he sees in the emergency room, “the vast majority of patients are cold. I don’t know how quickly a child drops to that temperature.” Prince’s temperature was taken at Prince William Medical Center about 20 minutes after he collapsed, and was 91.2. Bridges had testified earlier that he did not think that was unusual because small children cool off very quickly, particularly when their heart and brain are not regulating their body temperature.

Bellows then focused on the possibility that Prince was suffocated. Gormley, the chief medical examiner, said Monday he couldn’t rule it out as a cause of death, and that unless there were extraneous signs of it, “there are no pathological physical findings” for suffocation. He said it would take five to 10 minutes to suffocate someone to the point of irreversible brain damage.

“If a pillow were put over a child’s face,” Bellows asked Bridges, “with no signs of struggle … would it have to be kept on for the full 10 minutes, or is there a point where the child no longer has the capacity to breathe on its own? … How long before an individual of Prince’s size and weight would lose consciousness?” Bridges said his best guess would be five to six minutes, but that breathing would then possibly resume.

DiAngelo was asked on the witness stand last week if she had ruled out suffocation as a cause of Prince’s death. “His cause of death was drowning,” she answered. Defense attorney Chris Leibig asked if she were “medically able to rule out suffocation?” DiAngelo replied, “It was not the final event in this child’s life.”

The defense lawyers said they would rest their case Thursday. But Wednesday’s testimony may complicate the defense’s decision on whether to put Rams himself on the stand. The defense has not said whether the defendant will testify. He launched a website in 2013 to proclaim his innocence, but he has not spoken publicly about the case since a brief statement to The Washington Post in 2013, released through his lawyers, also saying he had not drowned his son.

Both the prosecution and defense decided in January to waive a jury, in part because of the technical aspects of the drowning case. Bellows, a former federal prosecutor for 19 years, also questioned another defense expert for more than 30 minutes last week. Rams is charged with capital murder, but prosecutors are not seeking the death penalty. He faces life in prison without parole if Bellows finds him guilty.

The chronology of Prince’s visit to his father’s home in Manassas, Va., as established by Jestice, Jestice’s wife, Sue, and Rams’s teenage son Joaquin “Shadow” Rams Jr., was that Rams and Shadow arrived with the boy on a visit from his mother’s home in Maryland about noon on Oct. 20, 2012. The toddler played with Shadow and the Jestices for about an hour, then went upstairs to the area where Rams and Shadow lived.

Shadow testified that Rams took Prince to Rams’s room, and that Shadow went to his own room to play video games. At some point, Rams summoned Shadow back to his father’s room to watch the toddler while Rams used the bathroom. He said Prince was snoring. Shadow then returned to his own room, and at some point Rams brought the toddler to Shadow’s room and placed him face down in a crib. Defense lawyer Joni Robin asked Shadow if Prince “seemed okay?” and Shadow said yes.

In a 2014 deposition in a civil case, a lawyer asked Shadow of this moment, “Could you tell whether Prince was alive?” Shadow responded, “At that point, no. I believe I did see him breathing at that time, though.” Shadow said in 2014 he went to the bathroom and when he returned, “I checked on Prince. He was still sleeping. And from what I could tell, he was still breathing.”

Meanwhile, Shadow testified last week, his father poked his head in the room twice to check on Prince. Then on a third visit, Rams burst into the room shouting Prince’s name, which startled Shadow because he hadn’t noticed anything wrong with the toddler. Rams rushed Prince to the bathroom, took his clothes off and told his son to get Jestice, according to Prince, or shouted to Jestice to call 911, according to Jestice and his wife.

Chief Deputy Commonwealth’s Attorney James Willett said in his opening statement to Bellows that he would rely on DiAngelo’s finding “to a reasonable degree of medical certainty, the cause of death was drowning” and that fluid in Prince’s body was “consistent with having placed the baby under running water in a tub.”

Bridges on Wednesday was the fifth defense witness to say that fluids administered to Prince by emergency personnel were possibly the fluids found in his lungs and intestines by DiAngelo during her autopsy, which she also cited for her finding of drowning. Eglal Shalaey-Rana, a pediatric radiologist at Children’s National Health Systems in Washington, said Prince was given 400 cc’s of saline solution about 45 minutes before his first chest X-ray, and another 400 cc’s was given before his second chest X-ray, which both showed cloudiness in the lungs, which could have been either fluid overload or aspiration from drowning.

Bellows then asked whether suffocation would show up on an X-ray. Shalaey-Rana said sometimes there were indications of pulmonary edema, or fluid in the lungs, or other “air space disease” after a known suffocation, but sometimes there were no indications.