Lagerblom v. Sweden, No. 26891/95, ECtHR (Fourth Section), 14 January 2003

Right to a fair trial. Person belonging to a linguistic and ethnic minority. Right to documents of the proceedings and oral discussion translated by an interpreter. 

Art. 6 ECHR

If a person, charged with a criminal offence, understands the language of the proceedings well enough for him/her to exercise his/her right to a defence, he/she cannot insist to have an interpreter appointed. This applies even when the person belongs to an ethnic and linguistic minority.

Bideault v. France, No. 11261/84, ECommHR (Plenary), 1 October 1986