Lindsay Clancy holdout juror says he had no doubt she deliberately killed her children
It is the first time the juror, who refused to side with the others and acquit Clancy, has spoken publicly about his decision.
The lone holdout juror in the trial of Lindsay Clancy has said he "didn't have any doubts" that she was criminally responsible for killing her three children.
"Based on all the physical evidence, key witnesses and what the prosecution presents, I thought it was enough proof that she knew exactly what she was doing and planned it," Michael Desronvil said in a statement to CBS News, the BBC's US partner.
The judge declared a mistrial on 4 September after the jury failed to reach a unanimous verdict following nearly 40 hours of deliberating.
Clancy admitted to the killings but her lawyers argued she had been suffering from postpartum psychosis. Prosecutors said the killings were calculated.
Warning: This article contains distressing details
The 36-year-old was charged with three counts of first-degree murder after strangling Cora, five, Dawson, three, and Callan, eight months, at the family's Massachusetts home before jumping out of the second-floor window.
To find Clancy guilty, jurors had to be unanimously convinced beyond reasonable doubt that she intentionally killed her children and that she did not do so as a result of postpartum psychosis, a rare and serious condition.
The jury - nine women and three men - considered a range of options including not guilty by reason of insanity, manslaughter and first-degree murder.
Several jurors have said following the mistrial being declared that the panel was ultimately divided 11-1 in favour of finding Clancy not criminally responsible.
Desronvil said he believed the evidence presented in court showed she had planned the killings.
"I didn't have any doubts," he said in a statement to CBS on Thursday.
"As I tried to explain different possible theories during deliberation, I kept getting cut off as if I had doubts based on the evidence presented."
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Paula Devlin, one of the other jurors, told CBS Mornings that the panel had spent several days trying to convince Desronvil to change his mind.
"We all worked together to convince ourselves once we got to that point where it was 10 to 2," she said.
The jury foreperson, a retired fifth-grade teacher, described not being able to reach a verdict as "awful" and an "emotional rollercoaster".
She told NBC that Desronvil had "admitted he had reasonable doubt", but as she started filling out the verdict sheets, he apparently said: "But I'm still not going to say that she's not guilty by reason of insanity."
Another juror told local CBS station WBZ-TV that most of the jurors had been "very firm in their stance" from the start and "the stand-alone juror was not the only one that was unwilling to see things from the other side".
But they added that because Desronvil would not "follow" his reasonable doubt nor offer logical reasoning for his position, they felt Clancy had not received a fair trial.
The identities of all 11 jurors have not been officially disclosed but in the US, once a case is over, any juror can choose to speak publicly about a case and their deliberations.
Patrick Clancy, the children's father and Lindsay Clancy's ex-husband, is due to speak publicly about the case in an interview with the CBS programme 60 Minutes on Sunday.
In it, he is expected to discuss his grief, his memories of his children and the conspiracy theories that have flooded social media since the trial began.
He said he still speaks to his children "all the time", describing it as "a way I stay connected to them".
During the trial, Clancy's defence team had attempted to use her being put on more than a dozen medications in the lead-up to the killings, as well as seeking help from a suicide hotline and an emergency room, as evidence of her psychosis.
Postpartum psychosis can involve hallucinations and delusions, and her lawyers argued that she was unable to understand the nature of her actions or distinguish right from wrong.
A forensic psychiatrist who testified for the defence said Clancy experienced a "command hallucination" and a "delusion of influence" when she killed her children.
However, her psychiatrist testified for the prosecution that Clancy did not show signs of psychosis during their sessions, while another psychiatrist noted that the condition was not currently recognised by the American Psychiatric Association.
Under Massachusetts law, prosecutors had to prove beyond any reasonable doubt that Clancy was criminally responsible for the jury to find her guilty. The defence did not have to prove her mental illness or lack of criminal responsibility.
