MORRISTOWN - A driver accused of causing a crash that killed a police officer last year has pleaded not guilty to aggravated manslaughter and vehicular homicide charges.

Twenty-nine-year-old Michael Cassella, of Howell, entered his pleas in court yesterday. He's charged in the Oct. 16 crash on Route 80 in Roxbury that killed Mount Arlington officer Joseph Wargo.

Morris County prosecutors say Cassella was driving under the influence of a controlled dangerous substance when he lost control of his vehicle. He then crossed the median and crashed into Wargo's marked police cruiser.

The 38-year-old married officer was on routine patrol at the time. He had served in law enforcement for 18 years and was a member of the Mount Arlington force for more than 10 years.

AP wire services contributed to this report.

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