A former border inspector pleaded guilty Monday to guiding hundreds of illegal immigrants through his checkpoint booth in exchange for cash payments from a smuggling ring.

Michael Anthony Gilliland, a 44-year-old former Marine and agent with U.S. Customs and Border Protection for 16 years, faces up to 35 years in prison when he is sentenced Jan. 12.

Prosecutors said Gilliland took between $70,000 and $120,000 since 2004.

Wiretaps described in court documents recorded Gilliland, who worked the graveyard shift, speaking in code with two female accomplices about his schedule and how many immigrants would be coming through his lane.

Gilliland has been under house arrest, monitored by an electronic ankle bracelet, since posting $750,000 bond earlier this summer.

Gilliland was among six people accused of coordinating smuggling operations and deliberately failing to record vehicles that ferried immigrants through border lanes under his supervision. He was arrested in June.

Four of the others also pleaded guilty Monday to charges related to the smuggling plot.

Prosecutor Stephen Tokarz said the sixth defendant had also reached a plea agreement and was expected to appear in court Wednesday.