The judge imposed the sentence on Eliezer Marquez Navedo in a courtroom in Fajardo, the eastern coastal city where he ambushed Sara Kuszak in February while she jogged alone along a remote road. She was about five months pregnant.
Marquez, 36, pleaded guilty last month to first-degree murder, kidnapping and two sexual assault charges. He did not face the death penalty because capital punishment can be imposed on the U.S. island only for federal crimes.
The slain woman's mother gasped, her voice thick with emotion, when told of the sentence.
"It's a matter of justice," Joan Lang said by phone from San Jose, California. "He had no reason being out and about on the streets. It's a tragedy it took my daughter to bring him down."
Marquez cried and bit his lips as a prosecutor read statements from Kuszak's fiance and several relatives before the sentencing.
Chief Prosecutor Obdulio Melendez said that Marquez cannot be considered for release "before he is 100 years old" because the murder, sexual assault and kidnapping sentences will run concurrently. He did not immediately provide a specific possible parole date.
The victim's fiance, Cheshire McIntosh, said that Kuszak's loved ones were "relieved to see swift justice served to this violent killer," but that Marquez should never be evaluated for parole regardless of his age.
"There must not be any parole for someone who has in cold blood murdered and desecrated a young, pregnant woman," McIntosh said in his written statement, a copy of which he sent to The Associated Press. "This case should have been for DOUBLE murder with no chance of parole!"
Kuszak, 36, who worked on sailboats and part-time in real estate and catering, lived in Savannah, Georgia. She was visiting the U.S. Caribbean island with McIntosh and friends, and the couple planned to marry in the Caribbean in March.
On Feb. 4, Kuszak was jogging along a road in Fajardo when Marquez stuffed her in his car. From the trunk, she made a frantic phone call to McIntosh and told him she was going to die. She was found dead with her throat slashed about an hour later.
Detectives said Marquez, who had bloodstains on his shirt and pants when he was arrested, admitted abducting Kuszak after seeing her jogging alone.
Kuszak's killing was similar to murders that Marquez's mother, Ines Navedo, was convicted of committing in 1992. She served seven years for slashing the throats of two young siblings aged 2 and 3 before being paroled.
Police have since reopened that case to probe whether Marquez may have been responsible. They plan to re-interview him and are analyzing the victims' wounds for any similarities, but Lt. Nelson Torres said the investigation has stalled because no witnesses have turned up.
McIntosh urged Puerto Rico to vigorously investigate Marquez's possible involvement in the 1992 slayings, saying a thorough probe is the only way "for true justice to be served."