But she sure plans to keep using it.
London's Metropolitan Police haven't had much success in using facial recognition tech, but they're not giving up, either.
The head of the Met Police, Cressida Dick, on Wednesday defended the controversial use of the technology even as she downplayed its effectiveness.
"It's a tool, it's a tactic," Dick said at a hearing before the London Assembly, The Register reported. "I'm not expecting it to result in lots of arrests."
The Met has used automated facial recognition technology four times this year and plans for five more before the new year, including by the end of this month, according to The Register.
However, the technology apparently hasn't been very accurate. A reported published by The Independent in May said that the facial recognition software used by the Met Police returned false matches in 98 percent of the cases.
"The Commissioner said that the technology is now beginning to move fast and is getting better. We are looking at ways it can be combined with other technology," a Met Police spokesperson said in an email statement. "She [also] noted that the government is engaging in thorough debates to balance privacy and security."