Judges aren't expecting you to have access to university research laboratories or be a Ph.D. candidate for the topic area you've chosen. What is important is that the technical level of sophistication and complexity of your project reflect YOUR level of understanding - not someone else's. It's OK to receive help outside your school as long as you clearly say what is was and who helped you. Chances are if it doesn't make sense to you, it won't make sense to the judge. If you can't explain it to a judge, then you probably don't understand the science of what's going on.
Judges look for complete projects.
That is, projects that are thorough in addressing the original question and thorough in answering other questions that come up during the experimentation process. As a scientist, it is your responsibility to provide all evidence to support whatever claims you are making. It isn't up to the judge or other scientists to prove your claim. Without data or results that support your claims, it's not a completed work. Either way, it will show.