Quality of Evidence Necessary for Preliminary Injunctions
The evidence at these hearings does not have to strictly comport with the rules of evidence generally, and so hearsay evidence is sometimes admissible to show that the plaintiff should get its sought-after preliminary injunction. Hearsay (with some exceptions) is testimony about what you heard another person say and is inadmissible under the rules of evidence.
Often in preliminary injunction hearings, the plaintiff will produce evidence from its own employees. These employees will give testimony which closely serves the interest of the corporation. Judges and Magistrates who hear such cases often view such evidence with a jaundiced eye, knowing that the employee is going to be doing everything he or she can to get the preliminary injunction. Judges and Magistrates know the bias inherent in such testimony, especially since the boss is likely to be sitting there watching them testify.
The best evidence comes from persons unrelated to the plaintiff, and who could not care less about the outcome of the preliminary injunction hearing. So if you are thinking about trying to get a preliminary injunction against someone you feel is misusing your trademark, and all you have is testimony from your own employees, you might want to get a bit more juice behind you before you go into court.