Arizona is known for its tough stance against illegal immigrants, but this week a jury here sent a strong message of rebuke to anti-immigrant vigilante groups as well, sentencing the leader of a border watch group to death for her role in the 2009 home-invasion murders of a 9-year-old Hispanic-American girl and her father.

Latinos in Arizona had decried politicians' lack of attention to the brutal slayings, contrasting it with the more intense reaction to the murder of a white rancher in Cochise County last March, allegedly at the hands of an illegal border-crosser.

The death sentence handed down Tuesday in Tucson is against Shawna Forde, a resident of Washington State who headed the Minutemen American Defense group. She was convicted Feb. 14 of first-degree murder for orchestrating the killings of Brisenia and Raul Junior Flores of Arivaca, Ariz., a small community just north of the Mexican border.

“I think that the nation as a whole sees us as the wild, wild West, that things like that are going to be OK with us,” says Angie Thomas, who sat on the jury. “And they’re not.”

The case has drawn back the curtain to reveal the dark side of the debate raging in Arizona over illegal immigration.

Ms. Thomas and fellow jurors were told during the trial that Ms. Forde and accomplices gained entry to the Flores home with the expectation of finding drugs there, which could be sold to finance Minutemen American Defense's border-control operations. Finding no drugs, the intruders made away with inexpensive jewelry but, prosecutors said, not before fatally shooting young Brisenia and Mr. Flores. Both victims were American citizens born in the US.

“I see Shawna Forde as someone who would have liked to have been the face of a movement,” Thomas says.

Arriving at the death sentence was difficult, Thomas says, but it was aided by a picture of Brisenia presented during trial that was etched in her mind: “A little girl, with bright red fingernails; she’s wearing a white T-shirt and turquoise-colored pajama bottoms. She’s on a love seat. It’s a perfect, innocent picture until you realize that half of her face has been blown off.”

Brisenia’s mother and Mr. Flores’s wife, Gina Gonzalez, was wounded during the shooting but survived. She testified that her daughter was shot point-blank as the girl pleaded for her life.

To some here, the lack of public attention to the double slaying has left a bitter taste. When rancher Robert Krentz was killed in Cochise County last March, politicians quickly demanded increased border security, says Carlos Galindo, a community activist and radio talk-show host in Phoenix, who followed the Forde murder trial closely.

“We have failed leadership: They won’t speak up, they’re silent,” Mr. Galindo says. “To not say that it’s tragic for a child to die – that leaves it as acceptable to continue harming immigrants or Hispanics here in Arizona.”

The Krentz murder, which remains unsolved, has been largely blamed on an unknown illegal immigrant. A month later, Gov. Jan Brewer signed Senate Bill 1070 into law to clamp down on people living in the state without legal status. A federal judge put on hold key provisions of the law, and it remains in legal limbo.

Jennifer Allen, executive director of Border Action Network, a human rights group, concurs with Galindo. “We didn’t see a commensurate response after the shooting of Brisenia and her father, calling for zero tolerance of hate crimes or anti-Latino violence or zero tolerance for anti-immigrant groups.”

But even amid Arizona’s heated climate over illegal immigration, shootings like the one that took the lives of father and daughter are relatively uncommon, Ms. Allen says.

“Tragically, more common is the complacency on the part of government officials to attack it at its heart and call it for what it is: that it’s hate crimes,” she says. “These are anti-immigrant groups that have violent undertones and overtones.”

William Simmons, a border expert and political scientist at Arizona State University, views the Forde case as an exception – one of someone on the fringes. Forde’s group is an offshoot of the Minutemen movement launched in Arizona.

“These fringe elements get in the way of having civil dialogue about these issues,” he says.

Forde’s codefendants, alleged gunman Jason Bush and Albert Gaxiola, are expected to go to trial later this year. They also face the death penalty.