Despite training and field experience that the location and spread between conducted electrical weapon (CEW) probes is important in establishing incapacitation, there have been no human studies which have systematically examined the relationships between probe spread and incapacitation. We have investigated this relationship with the TASER(®) X26. We have also developed and validated methodologies for prospective assessment of the effectiveness of CEWs in the incapacitation of highly motivated human subjects. Subjects (n = 30) had probes placed on the front or back with randomly varied spreads in accordance with recommended targeting zones. Subjects were motivated to complete the task of disabling the device or a dummy officer suspended ten feet away during the exposure while using a training knife. Subjects were rated on their progress toward goal success and on the extent of any incapacitation using two separate observer scoring panels: one consisting of experts in physiology and X26 technology, and another of veteran peace officers. Incapacitation by all measures was found to be a function of spread; generally increasing in effectiveness up to spreads between 9 and 12 in. There were notable differences between front and back exposures, with front exposures not leading to full incapacitation of the upper extremities regardless of probe spread. This is the first published study on a quantitative methodology for directly assessing the effectiveness of CEWs in human incapacitation. We have also validated and quantified for the first time in human subjects that establishing a minimal spread between X26 probes correlates to the extent of device effectiveness.