its pretty impossible for that to happen over the internet. the pixels are not there if the image was blown up it would be a mess to be able to trace something like that. the only thing that can trace is your printer that i have heard of so that they can catch people who make counterfeit money. but the technology is not there to blow up a picture that has been compressed for the internet. I have also taken about 4 years of school for photoshop so im pretty good about editing photos and nothing like that can be done from what i have learned.
The Exif data that is available in some images has been used in the past by police along with a string of other bullshit bits of so called evidence, to fool a judge into issuing search warrants.
Mostly the police don't use one piece of evidence to blugeon some judge into complying with their needs for warrants, they often use lots of little curcumstantial bits of nothing to create something.
So they will present something like this:
Code:
Manufacturer = EASTMAN KODAK COMPANY
Model = KODAK C310 DIGITAL CAMERA
Exposure Time = 1/64 sec [0.016]
F Number = 9/2 [4.500]
Exposure Program = Normal program
ISO Speed Ratings = 140
Exif Version = 0221
Original Create Time = 2005:01:28 16:49:17
Digitalization Time = 2005:01:28 16:49:17
Components Configuration = YCbCr
Compressed Bits per Pixel = 16/5 [3.200]
Shutter Speed Value = 599/100 [5.990]
Aperture Value = 433/100 [4.330]
Exposure Bias Value = 0
Max. Aperture Value = 433/100
Metering mode = CenterWeightedAverage
Flash = Flash fired, automatic mode
Focal Length = 5.90 mm
as collected from an image posted on a website, along with a shit load of other circumstancial bits of nonsense, and make claims that they believe you are the owner of that camera, and give guarantees that with this specific bit of evidence they believe they will be able to make a match between the camera data collected from the images on the site to the one in your possession. And through HD analysis they believe they will be able to recover the deleted images and thus prove it came from you etc etc et cetera...
Just another trick they use in manufacturing the criteria for warrants.
If you are concerned about the exif data in any images you post just open your image in a text editor, the EXIF information is usually near the top of the file, change the name of the camera to Mickey Mouse then save - easy peezy.