In order to show fraud, the party asserting it should have all the facts in regard to where, when, how, etc. as they are the ones whom the burden falls on. They must show exactly what fact was being misrepresented and when this occurred. Fraud is when a false representation is made to the USPTO or information was willfully withheld, it was known that this was false, and that registration would not have been issued by the USPTO if it knew this information was false. It is important to note that false information is not necessarily fraudulent. If the false information was submitted due to negligence, a misunderstanding, or inadvertently then it is likely not fraudulent. To be fraud there needs to be an intent to deceive. Fraud can be found where the applicant knew or should have known. In addition, someone bringing a fraud case to the courts must have clean hands, meaning they have not also engaged in inequitable conduct. When completing your trademark application remember to check and double-check it for accuracy and truthfulness.
This blog is not legal advice and is not specific to your application. You should always consult an attorney.