In 1982, Calvin Grant (plaintiff) had heart surgery. Over the course of the surgery, Grant received five units of blood supplied by the American National Red Cross (Red Cross) (defendant). Each unit of blood was from a separate donor. The Red Cross had screened each of these donors in accordance with its protocols. Its protocols in 1982 did not include screening for hepatitis C. At that time, scientists had not yet isolated hepatitis C as a virus; they had only identified that there was a form of hepatitis that appeared to not be hepatitis A or hepatitis B, which scientists called non-A, non-B hepatitis. People with elevated levels of alanine aminotransferase (ALT) had an increased likelihood of carrying non-A, non-B hepatitis. Consequently, if blood donors were tested for ALT, some potential carriers of non-A, non-B hepatitis might have been identified. However, ALT testing would have missed 70 percent of non-A, non-B hepatitis carriers and disqualified up to 30 percent of healthy donors through false positives. In 1989, scientists isolated the hepatitis C virus, and a blood test became available for hepatitis C in 1990. In 1993, Grant discovered that he was infected with hepatitis C. Blood samples confirmed that the source of Grant’s infection was one of the five blood donors from his transfusion during heart surgery 11 years earlier. Grant sued the Red Cross for negligence in failing to screen his blood donors for hepatitis C using ALT testing. Grant alleged that the Red Cross’s failure to test for elevated ALT increased his chances of being infected with hepatitis C by 30 percent. Given that the test had a 70 percent rate of failing to indicate hepatitis C, Grant conceded that he could not prove that the Red Cross’s failure to test for ALT was more likely than not the cause of his hepatitis C. Grant argued, however, that the Red Cross’s conduct deprived him of a substantial chance of not contracting hepatitis C and therefore presented a triable issue of causation. The trial court granted summary judgment to the Red Cross. Grant appealed.