Lawyer linguists are always Administrator (AD) level officials who may even be recruited at a higher level (AD7 instead of AD5) to attract most candidates, with the condition being that they must stay in their position for at least 3 or more years without being able to transfer to other EU institutions or positions. A legal diploma is required, along with the knowledge of at least two or three languages at a very high level so that they can carry out translations and revisions from multiple source languages. Lawyer linguists generally work for the Council of Ministers, the European Court of Justice or the European Parliament, though some other institutions may employ a few of them as well.
See also:
Lawyer, Translator, Interpreter, European Public Administration
Related link:
Tips and Tricks, EU Agency Selection and Recruitment Database