Can EXIF data tell whether a photo has been edited or doctored?

For straight out-of-camera JPEGs, you may want to expand the metadata & data review to include things like the Quantization Table Matrix, Chroma Subsampling, and Huffman Tables, all of which help to describe how the JPEG is encoded. For example a lot of cameras use 2x1 Chroma Subsampling, while Photoshop may use 2x2 Chroma Subsampling. In regard to JPEG decoding, JPEGSnoop is the only tool, that I know of, that examines and reports the various matrices and tables.

In some cases, attributes of a particular camera, such as the consistent location of hot pixels can be used to compare images for authenticity.

In regard to typical metadata, I find that it's not what is changed for a particular metadata field that is tell-tale, but what new metadata is added or what metadata is missing that should be there. Almost every photo editing software package (at least, that I know) adds new fields, frequently some form of XML. In some cases, e.g. MS Windows, metadata is mangled or removed. I find "EXIFTool -csv ..." to be very useful.

Combining all of the aforementioned items; JPEG encoding, specific camera attributes, an inventory of all the metadata, can give you some degree of confidence that a JPEG image is directly from the camera. Of course, a clever determined person could game all of that, but it takes a lot of careful work.