For the most part you can't, and you should assume any image you find is copyrighted unless it's specifically attributed as public domain.
Having said that, one service that does a image copyright search is PicScout.
After uploading an image by using either the drag and drop or upload feature, PicScout Search finds the image stored in the PicScout Platform and provides a link to the image’s license.
This seems to require the owner of the image actually registering it with PicScout, but hey it's one place to check.
Additional info on the subject: