Real photos can be taken from all the different views, environments and lights configurations. Some of them you just don't see in the image, all you see is the final result.
Hence there could be lots of real photos that could be nevertheless perceived as fake and vice versa.
It's almost impossible to say whether they are real or fake.
I have seen a lot of real photos that look quite unreal, and a lot of fake photos that look natural enough to believe they are real.
"forensic techniques" can give only "may be" answer and have very high false positive and false negative rates to judge reliably.
They can be used for a big bunch of suspicious images from one source, but never for individual images from different sources.