A casual language translation implies disrespect for the literacy of the participants, may contain wording that is not appropriate for formal written documents in that language, or could even be offensive. All of these problems violate the principle of respect in The Belmont Report, a principle that the IRB must ensure researchers uphold.
In addition, in order for consent forms translated into another language to enable informed consent by the prospective research subject, the translated consent form must communicate the essential elements clearly and correctly. A consent form that lacks these features violates the requirement that the researcher respect the autonomy of the potential participant, as stated in The Belmont Report, an essential principle of ethical research which the IRB must also guard.
Finally, a poor translation may stigmatize the research associated with the translated document, which may undermine the goals of the research and reflect poorly on this institution. This would be particularly insensitive for a university, such as CSUB, with a predominantly Mexican-American service area population.