Today's talker: Dutch government proposes knee lock to stop parolees from escaping by Toby Sterling

Dutch guards overseeing prisoners on supervised parole may soon have a new tool at their disposal: a robotic knee brace that sends an electrical impulse cramping prisoners' leg muscles if they try to slip away.

The Justice Ministry said Tuesday it planned to test the system later this year if parliament approves it. Ministry spokesman Wim van der Weegen said the system could be compared with wheel clamps put on illegally parked cars.

"If the prisoner sticks to the rules, he won't notice it," van der Weegen said. "But if he disobeys, then he can't run away."

Under the country's furlough program, some people convicted of serious crimes are seen as having a sizable risk of re-offending, so they are gradually reintroduced into society to test whether they are ready. First they are allowed only guarded visits to relatives. Then supervision is gradually relaxed until the prisoner is deemed ready for unsupervised parole.

After several prisoners on furlough slipped their guards and committed crimes including rape and murder, parliament in 2005 ordered the ministry to examine new ways of stopping them.

The system under development consists of a robust metal brace equipped with electronics. If a prisoner gets too far away from his or her guard, a wireless transmitter prompts the brace to send an electrical impulse.

The idea is to slow prisoners down in the first moments when they may use a distraction to try to bolt away from their guards.

Tracing chips also were considered, but van der Weegen said they were not as good as the knee brace for situations where the primary goal was to prevent prisoners from escaping, rather than tracking them after they had gone.

Van der Weegen said he expected the government to approve testing.

"There was a strong will within parliament to reform the furlough system" after the escapes, he said.

He added that other measures, including cutting back the numbers of prison leaves granted and increasing the amount of time that prisoners are kept under guard, already have been put into effect.