24 Hours in Police Custody: Child abuse officer reveals emotional toll
A police investigator said she has seen "the worst things imaginable" during her work to catch paedophiles.
Nicky Owen said she could not forget the faces of the children she had seen in abuse photographs, as she explained the emotional toll of her team's work.
"All these children that don't have a voice - we are there to stand up for them," she said.
Ms Owen of Bedfordshire Police is featured in the second episode of 24 Hours in Police Custody on Channel 4.
"There's not much that shocks me any more. I've seen the worst things imaginable," she told the BBC, describing the child abuse images seized from paedophiles.
"What could be more shocking than that? I can't think of anything.
"There's a particular girl... Her face always pops into my mind," the former bank worker said.
"It's just blank and empty and accepting of what's happening. No child should have that facial expression."
The episode follows Ms Owen and the Internet Child Abuse Investigation Team (ICAIT) as they arrest and question paedophiles.
Ms Owen admitted the emotive nature of the work posed challenges.
"When I'm sitting opposite someone saying it's not real, what they are looking at, or they are crying [and] making excuses... I can feel it bubbling up and I have this overwhelming urge to shout at them," she said.
"I need to stay calm, stay professional, get them to court and get them convicted."
The episode will be aired on Channel 4 at 21:00 GMT on Monday.