If you exert further pressure on the right from posterior to anterior with a right sided rotational adjustment, you will increase your susceptibility to creating a vertebral artery injury. For safety's sake, if you must adjust C-1, adjust it from the left side with a posterior left contact. The same applies to C-2. What I have presented is based solely upon my experiences with supine motion and static palpation procedures. Like everyone else who practices, experiences include successes and failures.
Failures are hard to look at and be objective about.
Fortunately, I have not had any lawsuits, nor have I seriously injured anyone. I do believe that mistakes are more related to poor choices in relation to the selection of cervical levels for adjustment and directions of applied force with adjustments. This could pertain to regular adjusting or low-force adjustments. References Chiropractic acquitted in Canada. DC Nov 2, 1998.