To answer this question, first we should define what "translation" is. Most people who are not language professionals often use "translation" or "translate" when they actually mean "interpretation" or "interpret." For example, in a medical setting a patient may request an "interpreter" to facilitate communication between her/him and the care provider. That interaction may very well include a document, form, brochure, website, text message, or any other type of written material that has been "translated." So therein lies the difference - interpretation is the oral/verbal form of communication in another language, while translation is the written rendition of a message.
So back to the bilingual employee mentioned in the heading. In the case of Spanish, about 50 million people speak Spanish in the United States, many of whom provide vital functions throughout the labor force (including translation). In some cases, these professionals were selected for their positions on account of their bilingual skills, or at least as an added asset. They also understand the company and possibly its customers better than any outside professional. Why then, should they not be relied upon for a translation task? Because there is a difference between speaking a language and being a language professional. You may speak a language, even as a native speaker, but that doesn't make you a language professional, an interpreter or a writer.
Translation is a profession that takes years to master. Language proficiency is acquired in two ways: through the community language we are all a part of, and through formal education. Many bilingual Spanish speakers in the United States meet the first of these two conditions, and they are often prime candidates to become excellent interpreters or translators. Many switch effortlessly from language A to language B and back to A, and have done so repeatedly and naturally since childhood. But if they want to be professional interpreters/translators they must learn the nuances of both languages (grammar, syntax, idioms, register, etc.) The study of specialized terminology is also required (legal, medical, technical). They must learn about state and local laws, as well as about confidentiality, cultural, and other ethical issues. In other words, in most circumstances bilingual individuals must enroll in a translation or interpretation program, which will commonly lead to a form of diploma or certification (American University in Washington DC has a great program!)
The scope of your translation project will also determine if your bilingual employee can help. As mentioned elsewhere on this blog, Germans have a wonderful term, Vieraugenprinzip - the "4-eyes" or "two sets of eyes" principle. Basically, it states that two people are required to review any task as part of a quality control/assurance process. Depending on their proficiency, your bilingual employee could very well be the "first set of eyes", while a professional translator can act as the editor/proofreader during the QA process. This process may be acceptable for a small translation task (short letter, social media post, etc.) - for larger and ongoing projects, trust a professional.
Do you have a translation project in mind, or would like to have a consultation? FullCircle Translation can help.