The judge in Los Angeles followed the recommendation of the jury that convicted Turner, 47, in June of killing Cynthia Johnson, Elandra Bunn, Deborah Williams and Mary Edwards.
Maxine Johnson told the Los Angeles Times she is glad her sister's killer will be "kept out of civilization."
"He did all the victims wrong," she said. "He's a monster."
All the killings Turner has been charged with occurred between 1987 and 1998, mostly in a narrow corridor along 30 blocks of Figueroa Street, a major artery in Los Angeles. The area at the time was known for drugs and violent crime.
Turner became a murder suspect after he was convicted of a violent sexual assault and required to give a DNA sample in 2003. His DNA was linked to two unsolved crimes, inspiring investigators to examine other cold cases.
In 2007, Turner was tried, convicted and sentenced to death for killing 10 women and the 6 1/2-month fetus of a pregnant victim.