The police force used facial recognition software to scan faces of those attending the Download music festival and checked them against a list of wanted criminals across Europe who target similar events.
It is believed to be the first time the software has been used at an outdoor event in the UK, and was described as campaign group Big Brother Watch as "worrying."
Chief superintendent Chris Haward dismissed these concerns, saying:
"The software provided an efficient and effective way of picking known offenders out of a crowd - something that officers would previously have been done using paper briefings," he said.
"While it is too early to give definitive crime figures, early indications are that it has remained low."
Police have said that if someone were wrongly identified, officers would "use their discretion appropriately."
Renate Samson, chief executive of Big Brother Watch told the BBC that the use of technology was "a great worry."
"We're very keen for bad people to be caught but we're also keen for innocent people to go about their day-to-day business, have a good time at festivals they've paid good money for, and not feel as though they're being surveyed by police," she said.
Thousands attended Download at Donington Park this year where Muse, Kiss and Slipknot headlined and a cashless payment system was trialled in an attempt to cut crime.
Download’s radio-frequency identification (RFID) wristbands, provided by German RFID specialists YouChip enabled people to pay for food, drink and merchandise.
The system crashed on 11 June and many registered their disgust on social media, which festival organisers described as "some minor technical issues, effecting around 1% of attendees."
There had been fears the wristbands would also be used to track people’s locations but the festival’s website denied this could happen as no GPS chip is included.
IT journalist John Leyden called the festival "a privacy invading tech test bed."
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