Lex Maria is the colloquial name for the mandatory reporting in Chapter 3 Paragraph 5 of the Swedish Patient Safety Law (Patientsäkerhetslagen). The law requires that a care taker report to the Health and Social Care Inspectorate events that could have caused or have caused serious injury to the patient.[1] The name originates from an incident in 1936 when four patients at Maria hospital in Stockholm died after being injected with disinfectant (mercury oxycyanide) instead of anesthetic.[2]