Regarding res ipsa loquitur, an inference arises that the defendant has been negligent when the accident causing the harm is a type of accident that ordinarily occurs through the negligence of the class of actors of which the defendant is a relevant member. In Ybarra v. Spangard the plaintiff was injured during surgery but did not know who was responsible. The court permitted res ipsa loquitur. [...]

The case See Summers v. Tice. presents an example of the alternative cause test in which two defendants both acted negligently but only one party could have been responsible and the responsible party cannot be determined. The burden of proof shifts to the defendant to prove who is responsible and therefore liable. [...]

Negligence may be established through circumstantial evidence and a party need show merely constructive knowledge, not actual knowledge. As per the pizza slip-and-fall case Jasko v. F.W. Woolworth Co., no notice requirement is necessary when the operating methods of a proprietor are such that dangerous conditions are continuous or easily foreseeable. [...]