Leather jackets can be durable, stylish additions to your wardrobe, but they can also be easy to damage. Because leather is made from animal skin, it's already porous, so a minor blemish can speed up the deterioration of your coat. Doing any work on your jacket can be delicate, particularly when you're taking out stitches that will leave needle marks on your coat. Removing sewn-on patches can be particularly difficult, since they're often glued as well as stitched to the jacket.
Turn the jacket inside out to check if the patch is sewn through the leather into the lining of the jacket. If it's not, find the seam where the lining is attached to the jacket.
Use your seam ripper to carefully remove the stitches that attach the lining to the coat. Turn the coat inside out so that you're looking at the backside of the leather. Find the stitches that attach the patch to the jacket.
Slide your seam ripper under each stitch as delicately as possible, and remove each individual stitch. Every stitch in the leather will leave a hole, so you do not want to make the hole any larger. You must remove every stitch before you can pull the patch off, or you risk ripping the holes.
Pull the patch off once you remove all the stitches. If it does not come off, the patch was in all likelihood put in place with both adhesive and stitches. Carefully pry up as much of the patch as you can, and spray WD-40 under it. Reader's Digest says that WD-40 will not only help remove adhesive, but will also condition leather too.
Apply a larger patch to cover the holes if they're too big or unsightly. Alternately you could use a leather repair kit to fix them.