Definition of Efficient intervening cause
An intervening efficient cause is a new and independent force, which breaks the causal connection between the original wrong and the injury and is the proximate cause of the injury. Thus, the original negligent actor is not liable for an injury that could not have been foreseen or reasonably anticipated as the probable consequence of his negligent act and would not have resulted from it had not the intervening efficient cause interrupted the natural sequence of events, turned aside their course, and produced the injury. Coyle v. Stopak, 165 Neb. 594, 86 N.W.2d 758, 768; Knuth v. Singer, 174 Neb. 182, 116 N.W.2d 291, 295. See also Proximate cause.
That's the definition of Efficient intervening cause in Black's Law Dictionary 6th Edition. Courtesy of Cekhukum.com.