The plaintiffs allege that Sutton Hill was negligent for having failed to diagnose and to treat Cahill while he was a patient. The plaintiffs' expert, Dr. Marc R. Shepard, whose qualifications were not challenged by Sutton Hill, opined that (1) Cahill "exhibited a number of symptoms that, combined with his exposure [to C. Diff] and risk factors [antibiotic use, prolonged hospital stay, advanced age, and co-morbid illnesses including his renal failure ] should have heightened suspicion for C-Diff"; (2) the standard of care in these circumstances required "that he be given appropriate and prompt diagnostic testing for C-Diff"; (3) once Cahill's white blood cell count became elevated, "the concern for the cause of [the] infection should have been heightened"; and (4) "[d]espite a clear deterioration in his condition, repeated complaints of soft and/or loose stools, nausea and chills, and laboratory studies indicative of infection, the staff did nothing to diagnose and treat his condition." Dr. Shepard ultimately opined, to a reasonable degree of medical certainty, that the failure of the Sutton Hill staff to diagnose C. Diff colitis allowed it to progress to the point where significant damage was done to Cahill's colon, and that the untreated colitis was a substantial contributing cause of Cahill's death.