SOUTH LAKE TAHOE (CBS13) – A South Lake Tahoe police officer pleaded guilty Wednesday to multiple counts of witness tampering and obstruction of an official proceeding.

A three-year, multi-agency investigation  involving the FBI led to 44-year-old John Gerald Poland’s arrest in January on five counts of witness tampering.

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According to court documents, Poland interfered with a June 2011 federal investigation of a known South Lake Tahoe gang member by persuading the gang member’s girlfriend to conceal and destroy evidence.

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In October and November 2011, Poland tampered with the witness once again during an investigation into his own conduct, as well as the gang member. Poland also had another witness conceal and destroy evidence.

The former police officer admitted to corruption charges of attempting to alter, destroy, mutilate, and conceal evidence material to an official proceeding.

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Poland cold face 20 years in prison for each count; sentencing is scheduled for August 7.