The aim of this paper is to raise the ethical problems which appear when hearing computer scientists work on the Sign Languages (SL) used by the deaf communities, specially in the field of Sign Language recognition. On one hand, the problematic history of institutionalised SL must be known. On the other hand, the linguistic properties of SL must be learned by computer scientists before trying to design systems with the aim to automatically translate SL into oral or written language or vice-versa. The way oral language and SL function is so different that it seems impossible to work on that topic without a close collaboration with linguists specialised in SL and deaf people.