A farmworker was sentenced on Monday to life in prison without the possibility of parole in the fatal stabbing of an Iowa college student in 2018, a crime that Donald J. Trump seized upon as president as he amplified his hard-line policies against illegal immigration.
The farmworker, Cristhian Bahena Rivera, was convicted in May in the abduction and murder of Mollie Tibbetts, 20, a University of Iowa student who disappeared after going for a run.
It took more than a month until Mr. Bahena Rivera led investigators to the body of Ms. Tibbetts, which had been hidden in a cornfield outside Brooklyn, Iowa, her hometown.
The arrest of Mr. Bahena Rivera, who had been described by the authorities as an undocumented immigrant from Mexico, quickly drew the attention of Mr. Trump. The president sought to use the case to his political advantage during the midterm elections in 2018 and in his efforts to build a border wall.
Mr. Bahena Rivera, 27, was expressionless as a caseworker with the state attorney general’s office read a victim impact statement on Monday that was written by Ms. Tibbetts’s mother, Laura Calderwood, in a district court in Montezuma, Iowa.
Ms. Calderwood said in the statement that her daughter had so much to look forward to until the evening of July 18, 2018.
“You chose to violently and sadistically end that life,” Ms. Calderwood said. “Who could harm such a beautiful, vibrant young woman so full of life and promise?”
Ms. Calderwood said that she would never recover from her daughter’s murder and from having to tell Ms. Tibbetts’s grandmother and other family members that her body had been found.
Because of Mr. Bahena Rivera’s actions, she said, Ms. Tibbetts’s boyfriend would never be able to give her the engagement ring that he had gotten for her.
“Because of your actions, Mollie’s father, Rob, will never get to walk his only daughter down the aisle,” Ms. Calderwood said. “Because of your actions, Mr. Rivera, I will never get to see my daughter become a mother.”
Mr. Bahena Rivera, who is planning to appeal his conviction, did not speak at the sentencing. His lawyers also declined to comment.
In Iowa, a conviction for first-degree murder carries a mandatory sentence of life in prison. Lawyers for Mr. Bahena Rivera tried unsuccessfully to argue that someone else had committed the killing.
During his trial, The Des Moines Register reported, Mr. Bahena Rivera testified that two armed and masked men had confronted him in his home and had ordered him to drive them to Brooklyn, where one of them killed Ms. Tibbetts, put her body in his trunk and ordered him to drive to a cornfield.
Judge Joel D. Yates of the Eighth Judicial District rejected that defense during the sentencing.
“Mr. Bahena Rivera, you and you alone forever changed the lives of those who loved Mollie Tibbetts,” Judge Yates said.
The judge also ordered Mr. Bahena Rivera to pay $150,000 restitution to Ms. Tibbetts’s family and denied him bond while he appeals his conviction.
Ms. Tibbetts, a psychology student and summer camp counselor, was raised in San Francisco and Brooklyn, a small town between Des Moines and Cedar Rapids.
According to investigators, blood that matched her DNA was found in the trunk of Mr. Bahena Rivera’s car, which had been captured on a home-security camera near where Ms. Tibbetts had been running.
Scott D. Brown, a special assistant state attorney general, called the evidence against Mr. Bahena Rivera “overwhelming” and said it supported a life sentence.
“Based upon the facts and circumstances of this case,” Mr. Brown said, “it is very well deserved.”