[citation needed] The T4 program was influenced by a popular book, Allowing the destruction of life unworthy of living, written in 1920 by Alfred Hoche and Karl Binding.
In his 1962 publication, Grenzsituation des Lebens (Border situations of life), Catel argued for the reintroduction of euthanasia.
"Real" euthanasia was seen as the killing of a person who was suffering from so much pain, that an ever-increasing amount of pain-reducing drugs had to be administered.
A 2024 investigation of Mammolshöhe by the Hesse State Welfare Association (Landeswohlfahrtsverband Hessen) found that Catel used his position to illegally experiment on children.
In addition, Catel recruited former colleagues from the Leipzig euthanasia program to Mammolshöhe, and investigations into his work were obstructed by other doctors, pharmaceutical companies and the medical bureaucracy.