"Factual basis" refers to the information or evidence that supports a statement or claim. It means having reliable facts or data to back up what you are saying or to prove something is true. Full definition
There must be, of course, a sound factual basis for doing so, assisted by directed argument from counsel. (slaw.ca)
They play to our emotional, not factual based decisions. (naiaonline.org)
Equally, where there is no allegation of contributory conduct ensure that the tribunal does not become distracted by issues relating to the underlying factual basis of the case, which may lead it to fall into this error. (newlawjournal.co.uk)