How do you judge a creepy investigation when the evidence is so unclear?

Start with the ordinary checks before drawing a conclusion. Keep the original photos and audio, look at the images in full resolution, and note the lighting, camera angle, reflections, and anything moving in the background. For audio, listen without looking at the questions that were asked, and see whether another person hears the same words. A sound that seems clear in the moment can be much less clear later.

That does not prove nothing unusual happened. It just keeps an ambiguous image or sound from carrying more weight than it can support.

If the group felt unsafe, leaving was enough of a reason to leave. There is no need to return to settle the question. If you do visit any cemetery, check that visitors are allowed, stay on paths, go in daylight, and avoid disturbing graves or entering closed areas. A buddy and a clear plan to leave are more useful than trying to push through fear for a better recording.

Some people may understand an experience like this spiritually, while others will see coincidence, shadows, or an audio device picking up unclear sounds. The details alone do not settle which explanation is right. If a farewell or protective ritual is meaningful to you, it can be a personal way to close the experience, but it is not something that can verify what caused it.

You can respect the place and still decide not to investigate there again.