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David Sweat arrives for his arraignment at Clinton County Court, in Plattsburgh, New York, Thursday, Aug. 20, 2015. Sweat and fellow inmate Richard Matt escaped from Clinton Correctional Center in Dannemora on June 6. Reuters

David Sweat, the convicted murderer who escaped a maximum-security section of an upstate New York prison in June but was later caught, had a not guilty plea entered on his behalf Thursday to the three new felonies he is charged with, NBC News reported. The not guilty plea was entered, as is required, because he declined to enter a plea himself.

Sweat was arraigned on charges of escape and promoting contraband. If convicted, he could get an additional seven-year sentence, although he is already serving life for murder.

He was ordered to be held without bail. Sweat was originally sentenced to life in prison after being convicted of killing a New York sheriff’s deputy in 2002. Broome County Sheriff's Deputy Kevin Tarsia was shot 15 times and run over, ABC News reported.

Sweat, along with convicted killer Richard Matt, escaped June 6 from Clinton Correctional Facility in Dannemora. The two convicts spent about three weeks on the run from police before they were found. Matt was shot to death while police attempted to capture him, and Sweat was captured two days later. Sweat was shot twice during his capture, CNN reported.

The two originally planned to go on the run with Joyce Mitchell, a prison worker who confessed to helping them escape by smuggling tools, such as a hacksaw blade, to them. Sweat and Matt were able to cut through prison walls to gain access to a series of hidden pipes.

Sweat would explore the tunnels at night after prison guards made their nightly cell checks, CNN reported. After a failed attempt to break through a concrete wall at the end of a piece of tunnel that led outside, the two escaped by crawling through a heating system, usually too hot to touch, that had been turned off for the season.