A court heard that Levi Ogden collapsed after being hit by the phone launched by Lloyd Birkby in downtown Halifax.
The 26-year-old woman suffered a cardiac arrest due to the impact of the phone causing bleeding in her brain.
Birkby, 27, who had a history of domestic violence against Mrs. Ogden, has now been imprisoned for five years at Leeds Crown Court.
The incident, which was captured by CCTV, occurred following an argument between the two men at a party in November of last year, said the judge.
Justice Geoffrey Marson QC said to Birkby, of Langdale Street, Elland, West Yorkshire: “You will have to take with you the knowledge that you have deprived the children of their mother.
“And it will undoubtedly affect them throughout their lives. “
Birkby acknowledged manslaughter at a previous hearing.
He appeared at the 35-minute hearing via video link from the prison.
Although the judge appeared, the two lawyers appeared via Skype and the journalists also followed the proceedings remotely.
The court learned that Birkby had a history of domestic violence against Ms. Ogden, serving a number of prison terms for battery, and that the police were called to their home about 20 times.
Prosecutor Dafydd Enoch QC said that the November 3, last year’s argument had developed between the accused and Mrs. Ogden, who was with his friend Courtney Bland.
Enoch said Birkby walked away but then returned to a “clearly angry state of mind.”
After kicking a passing taxi, he picked up a phone lying on the ground.
Mr. Enoch said that Ms. Ogden was about 6 to 8 feet apart when Birkby threw the phone “as hard as he could”.
He said that Mrs. Ogden faltered for a few seconds and then “collapsed into a heap on the ground.”
The prosecutor said that Birkby assaulted Ms. Bland and continued to act aggressively toward two Street Angels, who came to help, and the paramedics and police who arrived at the scene.
He said that the force of the blow and the violent twist of Ms. Ogden’s neck had caused bleeding in her brain.
Enoch described the situation as a “tragic and violent incident”.
Stephen Wood, in defense, told the court that this was a “very unusual” case.
He said it “could not be reasonably expected” that Birkby’s actions would result in the death of his partner.
Wood also told the court that his client was 11 years and five months of mental age.
Birkby was sentenced to two months in jail for assaulting Ms. Bland for the death penalty along with the five years of manslaughter.
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Justice Marson told him, “It is clear that you pose a significant risk of harm to future intimate partners. “
Detective Inspector Natalie Dawson of the West Yorkshire Police said: “This case is a tragic reminder of all that can happen when excessive force is used to try to resolve a situation. Levi’s death was completely unnecessary and demonstrates the perils of those resorting to violence.
“We welcome today’s sentence and hope it can end Levi’s family knowing that the man who caused his death is now behind bars. “