Essex is one of only four forces in the country to use polygraph testing to help manage the risk posed by convicted sex offenders.
It is used alongside a range of tools and tactics to gather information to provide an accurate assessment of the risk of re-offending.
In a first for the force, officers secured a sexual harm prevention order (SHPO) against one offender, which includes a condition that he must submit to a polygraph test when requested to do so by a police officer or delegated officer.
Detective constables Karen Halford and Ned Kelly, from the Management of Sexual Offenders and Violent Offenders (MOSOVO) team, completed an 11-week course to become trained polygraph examiners.
In one case, detectives referred a man with previous convictions for indecent exposure for the test after monitoring visits and intelligence gave cause for concern.
He agreed to take part and when questioned about the results of the polygraph, he admitted he had reoffended.
Following further work by detectives, a court application for a SHPO was granted in May.
One of the conditions the offender must meet is to take part in polygraph testing when requested to do so by a police officer or delegated officer. If he refuses, it will be a breach of the order and he will be arrested and interviewed.
Police will then take appropriate action, which could include being put back before the courts.
Detective Chief Inspector Jim Sandford said: “We use the polygraph test to get information about whether or not a sex offender is reoffending, so that we can assess the risk they pose to the public and ensure they are complying with sexual harm prevention orders imposed by the courts.
“We can t force people to take part unless it forms part of a court order and the results of a polygraph test can t be used as evidence in court.
“But the benefits are that it shows they are willing to engage and cooperate with the authorities, and it can prevent us relying on more intrusive methods of monitoring.
“The polygraph examination itself is carried out in three stages, with an interview, followed by the polygraph test and a post-test discussion.
“We have seen some participants tell us about reoffending during the pre-test interview and others make admissions after undergoing the polygraph.
“We have had occasions where offenders have admitted further offences or breaches of preventative orders, which have triggered investigations that are ongoing.
“We have also seen some admit that they may have potential contact with children, which has allowed us to directly intervene and keep people safe.