The Sacramento Sheriff's Department, which has been spearheading the investigation into the murder of Jessica Funk-Haslam, 13, said parental consent was not required in the DNA collection and interview of minors, several of whom were taken out of class during the day last week at Albert Einstein Middle School.
"These are interviews, not interrogations," Sheriff's Deputy Jason Ramos told ABCNews.com. "They are all consensual. Once it's done, there is a mechanism in place for school administrators to notify parents."
Ramos said the DNA collection was done at the time of the interview so efforts didn't have to be "duplicated." Ramos cautioned that the collection did not necessarily mean authorities had a DNA profile of the suspect.
Over the past few weeks, police have sifted through a number of leads and alibis but have been unable to name a suspect in Jessica's murder.
The teen's body was found at Rosemont Community Park on the morning of March 6. Jessica was reportedly arguing with her mother the night before and voluntarily left her home and boarded local transportation to a local park.
There is nothing under California law that prohibits DNA collection of consenting minors, said John Myers, a professor at the McGeorge School of Law in Sacramento.
"I think the answer is, kids can consent, and if they consented and it was knowing and intelligent, [law enforcement] can do the search," he told the Sacramento Bee.
Ramos said last week's DNA collection was not the first time detectives visited the school and that he expects they'll be back for more follow-up.
He declined to say how many students have been interviewed, but said students who spoke with detectives were sent home with contact information to give to their parents.
"The parents have been completely supportive of it, in fact advocating our detectives do that for the benefit of excluding their children," Ramos said. "We've gotten a lot of positive feedback."
But one parent who said her son was interviewed wasn't happy with the process.
"My child's in a room with two detectives being questioned and grilled and I'm sure he was quite frightened, which is very upsetting," Michaela Brown told the Los Angeles Times.
Gabe Ross, of the Sacramento City Unified School District, said the school immediately made efforts to notify parents by phone and also sent home a letter. However, Ross said the school would not stand in the way of the investigation.
"We're not in a position to interfere in any way with the law enforcement investigation. If and when law enforcement wants to interview our students, we inform parents immediately," Ross said.