Wurtzel bought a cup of coffee in her local Starbucks and placed it in her car's cup holder. While making a turn shortly after leaving the store, the lid came off the cup and the liquid spilled over Wurtzel's right leg, burning her severely. Wurtzel never looked to see if the lid was on correctly and did not see the coffee spill or the clerk secure the lid to the cup. She sued Starbucks for negligence, invoking the doctrine of res ipsa loquitur.

Was Starbucks clearly negligent without any need for witnesses?

Who else may have been negligent?