Ann Marie N. (plaintiff) filed suit against the City and County of San Francisco (the city) (defendant) after discovering that Mathew N., the child she had adopted through the city’s department of social services, was infected with the human immunodeficiency virus (HIV). Mathew’s natural mother routinely used cocaine and alcohol and engaged in prostitution. After his mother’s custody and parental rights were terminated, Mathew was placed with Ann Marie, who was aware that Mathew had been exposed to cocaine and alcohol during birth. Shortly after the placement, Ann Marie took Mathew to a pediatrician, who did not test Mathew for HIV but would have done so if Ann Marie had known that Mathew’s mother was engaged in conduct that might have exposed her to HIV. Six years later, a social worker for the city informed Ann Marie that Mathew’s birth mother had died of acquired immunodeficiency syndrome (AIDS). Mathew subsequently tested positive for HIV. At trial, Ann Marie alleged that the city was liable for negligence in breaching a duty owed to Ann Marie as a prospective parent to identify and test children at high risk for exposure to HIV and convey the results to prospective parents. Ann Marie also claimed the city had intentionally misrepresented Mathew’s health, as Mathew was in fact infected with HIV. Finally, Ann Marie alleged that the city had knowledge of Mathew’s medical condition and intentionally concealed the condition. The trial court granted the city’s motion for summary judgment, dismissing the claims for negligence and intentional misrepresentation. During a hearing on the intentional-concealment claim, a social worker for the city testified to being aware that Mathew’s natural mother had engaged in behavior that could have exposed her to HIV. The trial court granted the city’s motion for nonsuit. Ann Marie appealed.