Back translation is a very effective, very stringent quality process which is often used in medical translation. In a standard translation process, the translator translates the document; an editor then reviews the translation and makes corrections. A more robust process involves back translation, in which a second translator translates the foreign language document back to the original language. The original and back-translated versions are compared in order to validate the accuracy of the translation and to avoid mistranslations, missing text and other translation errors. Click here to read an article I wrote a while back on the subject of back translation.
Machine translation software, like Google Translation and Microsoft Translator, can be an effective way to validate a human translation. Just take the translation you received from a translator and use one of the automatic translation software programs to back translate it into the original language. The back translation may not always be high quality, but it will certainly allow you to test for missing words or mistranslations.
One of the good things about using MT for translation quality control is that it is free. It also allows the editor to suggest an alternate translation to the one used by your translator. But most importantly, it allows someone who does not even know the target language to apply some quality control to a translation. For example, say that you ordered a translation from English to German and do not know much German. Using MT for back translation will allow you to keep your translators honest by checking the work without having to assign a linguist to review the work.
Disclaimer: A back translation obtained using machine translation software may be incorrect. But even when this is the case, it never hurts to have your translator check a certain sentence again to see if it can be improved. The purpose of Quality Control is to improve the quality of a translation. And using MT for back translation can often help improve quality.