L30 Controller described a pilot deviation event when an air carrier on the SHEADS departure started an incorrect turn; was advised but continued; resulting in a close MVA infraction.

Narrative

While working Daggett RADAR departure sector; Air Carrier X called airborne climbing to 7000. I issued RADAR contact to Air Carrier X. I could not give him a higher altitude because of arriving traffic on downwind descending to 8000. When Air Carrier X was over REBEL way point he started his left turn as I expected him to. However; instead of turning to ROPPR way point as the SHEAD5 DP calls for; he appeared to be heading directly towards SHEAD way point and towards a 10;000 MVA at 7000. I issued an immediate left turn to 150 degrees away from the 10;000 MVA and advised him he was off course. He replied that he was on the SHEAD5 DP. I advised him that he was 7 NM West of ROPPR heading towards high terrain. Noticing no turn; I again issued a left turn and after clearing the downwind traffic issued a climb to FL190. After turning him to SHEAD way point when he was above 10;000; I transferred him to ZLA16. Recommendation; brief this pilot to turn his aircraft when told he is off course and do it immediately when told to do so immediately by ATC.