MILFORD (CBS) – The case against an illegal immigrant accused of drunk driving and killing a man could fall apart. An important witness apparently cut off his monitoring bracelet and left the country.

The family of Matthew Denice is furious. They were hoping the witness, Luis Acosta, would help put the man charged with hitting and killing their son in prison.

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Nicolas Guaman was driving through downtown Milford in a pickup truck when police say he struck the 23-year-year-old, who was on his motorcycle.

WBZ-TV’s Diana Perez reports

Immigration officials are blaming it on a technical mistake on the part of their outside contractor in charge of monitoring the bracelets.

Apparently Acosta, an undocumented immigrant, cut off his monitoring bracelet five days before the feds told anyone on the local level.

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Now there’s a good chance he is back home in Ecuador.

Milford Chief Thomas O’Laughlin and Representative Richard Neal were joined by Matthew Denice’s mother and stepfather at a press conference Monday.

They say Acosta cut off his ankle bracelet on October 1, but immigration officials failed to tell Milford police until officers called them on October 6th.

WBZ NewsRadio 1030’s Lana Jones reports

By then, they pinged Acosta’s phone and it came back at a terminal at JFK Airport in New York, where flights depart straight to Ecuador, Acosta’s home country.

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Rep. Neal says he is calling of the Department of Homeland Security and more specifically Janet Napolitano to figure out what went wrong.