I understand the theory and I certainly agree resaving jpegs will reduce the error level. If you have an undoctored image to compare it to, you could probably u

I understand the theory and I certainly agree resaving jpegs will reduce the error level. If you have an undoctored image to compare it to, you could probably use that to determine which parts have been changed. But given only an image that may or may not have been doctored the error level will vary so much with the image content that it won't be meaningful.