What is the test for a claim under the Eighth Amendment against a prison official for failing to prevent harm?

unconstitutional prison conditions). For a claim based on a failure to prevent harm, the inmate must show that he is incarcerated under conditions posing a substantial risk of serious harm. Helling v. McKinney, 509 U.S. 25, 35 (1993). The subjective element requires a showing that the defendant acted with a sufficiently culpable state of mind.

"[A] prison official cannot be found liable under the Eighth Amendment for denying an inmate humane conditions of confinement unless the official knows of and disregards an excessive risk to inmate health or safety; the official must both be aware of facts from which the inference could be drawn that a substantial risk of serious harm exists, and he must also draw the inference." Farmer v. Brennan, 511 U.S. 825, 837 (1994).