Court records show 20-year-old Benjamin Rutkowski entered his plea Wednesday in Provo's 4th District Court.
Rutkowski faces no more than a year in jail at his Oct. 17 sentencing on the misdemeanor charge.
The second defendant, 21-year-old Kai Christensen, has yet to enter a plea and has an Oct. 3 court date.
U.S. Forest Service officers say the two men set the traps in May in a canyon trail near Provo. One trap was rigged to send a 20-pound, spiked boulder swinging at head level. The other was designed to trip a passer-by into a bed of sharpened wooden stakes.
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