CHARLOTTE, NC (WBTV) - Police know electronic monitoring is not a perfect system, they often call it a "strong band-aid."
Two cases this week highlight the imperfections of a system that can track hundreds of offenders down to their exact location within seconds.
The Charlotte Mecklenburg Police Department is currently looking for Salvador Marquez who was already on probation for a robbery conviction. He was on electronic monitoring after being recently arrested and charged for property crimes.
Marquez was due in court this week and failed to show. Police say he cut and run.
Catrell Holloway is another offender who was on electronic monitoring, when he was arrested for another armed robbery. Mecklenburg County Jail records show Holloway was ordered to be on EM as a condition of his bond at least four times in the past two years.
Police say if an offender, like Holloway, does commit another crime while wearing a monitor, they can track the offender's location and match it to the crime.
Sergeant Dave Scheppegrell who oversees the unit calls it a success, despite cases like Holloway and Marquez.
Last year CMPD had 956 people on EM. Of those, 20 offenders cut and run, 35 re-offended, and 59 failed to comply with supervision orders.
Scheppegrell says there are currently 600 people sitting in jail, who if they make bond, would be placed on EM.
One of them would have been Demetrius Nathaniel Thomas. He's the accused robber shot by a Subway clerk in north Charlotte last week. Police say his accomplice, Jamal McKenith, was killed.
Thomas was ordered on EM last year for two separate armed robberies.
But those cases were dismissed. Thomas was just freed from jail a few days before the Subway shooting. Without any pending charges, he could not be placed on EM.