What is the test for establishing that an inmate has been exposed to unsafe levels of arsenic?

Perhaps of even greater significance here, in addition to establishing that his medical needs are related to unsafe levels of arsenic, plaintiff must also show that Defendant acted with deliberate indifference in exposing him to that unsafe condition. See Estelle, 429 U.S. at 104. Deliberate indifference is established only where the defendant subjectively "knows of and disregards an excessive risk to inmate health and safety." Toguchi v. Chung, 391 F.3d 1051, 1057 (9th Cir. 2004) (internal citation omitted). Because the deliberate indifference analysis is subjective, expert testimony is neither necessary nor significantly useful in determining whether Defendant acted with deliberate indifference. Expert testimony would not be admissible on the question of Defendant's state of mind.