Experimental research and analysis was focused on developing a lower neck rear impact injury criterion. Development was based on correlations between spinal kinematics and lower neck loads obtained using human cadaver intact head-neck complex specimens. Kinematics were significantly dependent (p<0.05) upon gender and spinal level. Anterior-posterior shear force demonstrated highest correlations with localized facet joint motions at C4-C5 through C6-C7 for both genders. Correlation slope was greater in females. Lower neck shear force had high predictive ability for lower cervical facet joint motions, a likely culprit for injury in low-speed automotive rear impacts. Due to gender-dependence, the injury criterion should incorporate a scaling factor for females.