The fingerprints on her back could be frome anything. It could be from pushing her down before smashing her on the head with the hammer, could be from rolling her body over to make sure that she was dead, or from someone else coming in to find out if she was alive or dead. That being said, I'd like to ask whether the body was found face up or face down, since this will help to figure out if the fingerprints on her back mean anything.
Any prints on the hammer don't necessarilly mean anything. It did belong to someone, and was therefore used as a hammer (we think) more knowledge about the tool, such as wear and tear on the head of the hammer would help us on getting a better idea of the age of the hammer, since if it has been used for hammering nails there will be small dents from the impact of the hammer against the head of the nail. Fingerprints on the hammer don't necessarily mean anything if the hammer has been used for hammering nails, since he may have lent it out to other people, adding more fingerprints to the hammer, along with the owner's fingerprints, also the fingerprints of the person who sold the hammer to the owner.
Azure was angry, however, from what I remember off the first page, he was drunk, and at a bar. If he was at the bar, the bartender would remember him, and drinking could be what happened as a result of this "affair".