By Carol D'Auria

NEW YORK (CBSNewYork) — A city correction officer charged with killing his ex-girlfriend nearly 11 years ago has pleaded not guilty to second degree murder.

Police say Christopher Clavell, 46, of Staten Island, was arrested Monday while in uniform at Bellevue Hospital where he worked.

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Clavell had been suspected from the beginning in the gruesome murder of his girlfriend Barbara Perez, 30. Perez was shot in the head on Aug. 11 2000 while opening the Ridgewood gym where she worked.

The couple was involved in a child custody dispute at the time of the shooting.

Clavell was questioned at the time but was not arrested.

The Queens District Attorney’s office took another look at the statement Clavell made to detectives on the day of the murder. It is now evidence against him.

Clavell, who has been a correction officer for nearly 21 years, has been suspended from his job. He is in protective custody at Rikers Island.