A driver whose speeding car killed a young mother was not prosecuted because he may have been temporarily insane at the time, a court heard.
David Johnson had sought a judicial review of a decision not to charge George Steele, who hit his wife Lauren, 33, in Merseyside, in October 2016.
The Crown Prosecution Service (CPS) said Mr Steele was in a "daze and unresponsive" due to illness.
Judge Mrs Justice Yip said it was rational not to prosecute Mr Steele.
The High Court heard Mrs Johnson died when Mr Steele's Toyota Auris hit a van and veered along the pavement driving at 50mph in a 20mph zone on College Road, Crosby.
Mr Johnson, 38, who had two children aged two and eight months at the time of the crash, sought a review of the CPS decision not to prosecute.
Mrs Justice Yip said: "On the face of it then, this was a clear piece of dangerous driving which caused the death of Mrs Johnson."
But she added the CPS said there was evidence Mr Steele was "in a daze or unresponsive" before the crash and might have been suffering from "insane automatism".
A medical expert said an MRI scan after the crash revealed "hardening of the arteries" and "infarcts of the brain", added the judge.
The CPS decided that Mr Steele would have been cleared by reason of insanity.
Mr Johnson claimed the CPS had misunderstood the medical evidence.
But the judge said the CPS had considered all the available evidence, including dash-cam footage, eye-witness accounts and a forensic collision report.
It concluded there was "strong support" that Mr Steele had no control over his driving from moments before the first collision.
Mr Johnson "fundamentally disagreed" with that conclusion.
The judge said: "The accident was an unimaginable tragedy for Lauren Johnson's family. She left behind two very young children."
She added: "Looked at in a broad common-sense way, the decision was rational and lawful."
"The CPS did not ignore the seriousness of the offence or the impact on the family and wider community."