If you were required to wear an ankle bracelet tracking device for electronic monitoring purposes, can you imagine how the conversation with police or probation officers would go if the device falsely notified them that you had tried to tamper with the strap to remove it?

It’s doubtful you would be believed if you tried to blame it on glitchy or defective technology. Yet in the U.K., some offenders may have been wrongly sent back to prison after defective ankle bracelets alerted the authorities that they had been tampered with.

The U.K. government admitted that ankle bracelets “used to electronically monitor offenders and suspects with a curfew” may have given false tamper reports to authorities and resulted in some people being wrongly imprisoned.

Apparently there had been in increase in the number of tamper alerts, indicating offenders were trying to interfere with the electronic monitoring equipment. The Ministry of Justice contacted EMS Capita, the provider of the monitoring service, and G4S, which supplies the straps and electronic tags.

The investigation by G4S blamed the problem on a “manufacturing defect,” specifically the strap fasteners on ankle bracelets that went into circulation October 2016.

Sam Gyimah, Ministry of Justice, said in a written statement to Parliament, “There is a small chance that some enforcement action may have been taken against an offender or suspect in response to a false report of a tamper. It does not mean an individual will have been automatically sent to custody. A single tamper alert without any additional evidence of an escalation of risk is likely to result in an alternative outcome, such as a warning letter. So it is unlikely that a first tamper on its own will result in an offender being recalled.”

1% of tracking devices has faulty straps

G4S issued a statement claiming that 115 tags, or about 1 percent, had faulty straps: “We undertook testing of sample straps in February and cross-referenced that with our production audit trail. We identified a manufacturing defect in approximately 1 percent of two specific batches of tag strap clips [fastenings].” The company went on to say it had rectified the problem and the faulty monitoring devices posed “no risk to the public.”

According to The Register, British politician Tim Farron called the issue a “colossal blunder.” Farron added, “People may have been wrongly sent back to prison because of this government's sheer ineptitude. A review is urgently needed to ensure this doesn't happen again.”

G4S, The Register noted, is one of the companies currently being investigated by the Serious Fraud Office “for overcharging the government the electronic tagging of offenders.”

Farron added, “The government can't seem to even do the basic job of keeping an eye on convicted criminals. Yet they have given G4S another contract. What are these people doing?”

The U.K. government is in the process of removing or replacing all potential faulty straps. If no tampering alert was registered, the government considers the device to be normal. A device with a faulty strap “could incorrectly register that somebody has tampered with it,” and the government said it will continue to monitor the electronic tracking devices and respond to tamper alerts.

The $516 million electronic tagging program was previously flagged as “red,” The Register said, which is “the highest risk rating available.”