The long-standing statute - common in many states but unavoidably controversial because of its connections to the abortion issue - was not often needed, prosecutors said. It's only the second time in 15 years that prosecutors in Chester County have applied the charge. Montgomery and Bucks Counties have used it once. Officials in Delaware County said they couldn't recall it ever being used.
Still, several prosecutors said they wouldn't hesitate to use it.
"You take your victims as you find them," Chuck Gaza, chief of staff at the Chester County District Attorney's Office, said last week as he left a preliminary hearing where he filed the third-degree murder charge against Simmons.
Police said Simmons, of Boothwyn, Delaware County, had been drinking for hours by 1:30 a.m. March 8, when he was driving on Wilmington Pike in Birmingham Township, and his car crested a hill going 113 m.p.h.and rear-ended McQueen's vehicle.
The force sent McQueen's car airborne into a snowbank; it then bounced into the air again, slammed into a telephone pole that sheared off, and kept going, police said. McQueen was ejected through the sunroof as the car flipped over before coming to rest upside down.
An officer at the scene testified at Wednesday's preliminary hearing in Kennett district court that Simmons was furious with officers, demanding medical treatment repeatedly, even after he was told the only available ambulance was for McQueen.
McQueen and members of her family declined to comment in court Wednesday. Police said she had lingering health issues from the crash and doesn't remember anything from that night, when she suffered a concussion.
Simmons, who is free after posting 10 percent of his $100,000 bail, declined to comment through his attorney, Evan Kelly.
Gaza said the case marked the second time his office had charged someone with killing an unborn child.
The Pennsylvania law has been in effect for 15 years. Similar laws have been passed in 38 states, and a federal version was passed in 2004, shortly after the highly publicized killing of Laci Peterson, whose husband, Scott, was convicted of murdering her and their unborn son.
Abortion-rights advocates have long voiced concerns that the law is part of a backdoor strategy to appeal Roe v. Wade on the ground that states are upholding fetuses' right to life. They have said states should instead pass enhanced penalties for crimes against pregnant women.
More recently, they expressed concern about the law's being used against women, such as a 2010 case in Indiana in which a woman was charged with murder after a failed suicide attempt allegedly led to the death of the baby she was carrying.
Pennsylvania's law exempts pregnant women from criminal liability.
Before Simmons was charged, the law was last used in Chester County in the 2002 strangling of a pregnant woman, Gaza said. In Philadelphia, defendants have been charged with killing unborn children 13 times since 2008, according to Tasha Jamerson, spokeswoman for the District Attorney's Office. She said a charge of aggravated assault on an unborn child was more common, though was still infrequently used because prosecutors have to prove defendants intended to harm the child.
Kevin Steele, first assistant in the Montgomery County District Attorney's Office, said he prosecuted the county's only use of the murder statute in the 2005 shooting of Jennifer Pennington in Fairmount Park.
In Bucks County, it is being used for the first time in the 2013 killing of Ebony Capri Talley, who was pregnant, and her 4-year-old son. The defendant, Marcel Johnson, faces three counts of murder.
The prosecutor, Matt Weintraub, said there was no discussion - "Never even a debate. Not internal. Not external." - about whether to move forward with the charge for the unborn child.
"If she had been one day pregnant, and I could prove it, I would still be prosecuting this case," he said.
Under some fetal homicide laws, that wouldn't be possible. In Arkansas, the fetus must be past 12 weeks gestation for the law to apply. In Indiana, the threshold is that the fetus must have attained "viability." Under most laws, including Pennsylvania's, the fetus is protected from the time of conception.
Steele said for that reason he was surprised the charge wasn't used more often. But homicides in his county are unusual, he said, and men are more commonly victims.
Weintraub said use of the charge was low in Bucks County for probably the same reason.
"It surprised me a little bit," he said of realizing his current case was unprecedented in the county. "It's a long time to not have needed to use that charge, but I guess in a way I was relieved."