They must be able to prove that a dangerous condition existed on the premises. A dangerous condition is typically obvious – a vicious and unchained dog, a broken stairwell or defective escalator, or a crumbling balcony. It does not include unforeseeable conditions that injured a guest. The person or company that controlled the property where the injury occurred must typically be aware of the condition. However, the law does not always require the property owner or occupant to have actual knowledge of the condition.