Ill-treatment of an individual ‘must attain a minimum level of severity’ if it is to fall within Article 3. (…)
Also relevant is whether the victim is within a further category, which overlaps with those listed above, of persons who are ‘vulnerable’, including the elderly, minors, asylum seekers, and persons in detention. (…)
A state may be responsible under Article 3 for the acts of its servants or agents that are ultra vires. (…)
In contrast with torture, inhuman treatment need not be intended to cause suffering and there is no need for the suffering to be inflicted for a purpose. (…)
Mental, or psychological, suffering by itself has been found sufficient in several contexts. (…)
In another case, the Court stated that the “terrifying experience’ of those present when armed and masked police officers burst into their home was in principle inhuman and degrading treatment.
The mental suffering caused to an individual by the ill-treatment of a close family member may also be in breach of Article 3.
D. J. Harris, M. O’Boyle, E. P. Bates, C. M. Buckley
(Law of the European Convention on Human Rights, Oxford University Press, august 2018, la pp. 238-9, 243-4)