Jekyll could not have been purely innocent, because he chose to create a drug that would intentionally pull out his evil side. Furthermore, we may all have a darker side, but we don't all go on killing sprees. It is safe to conclude that Dr. Jekyll wanted to have a murderous personality all along, but he was too shameful to show this side of himself in society, so he instead created a manner in which he himself could commit the murders, but without showing the general public who was truly behind them. Dr. Jekyll and Mr. Hyde looked and spoke differently, even though they were derived from the same person, so people who ran into them had no idea they were actually speaking to the same person.
The downside to Dr. Jekyll's plan is the fact that he had no real control over when or how often he would turn....
It is also uncertain if he had any control over who would die or the manner in which they were killed. Dr. Jekyll and Mr. Hyde seemed to know what the other had been doing, but it is not completely clear that when one turned into another, both "men" felt and experienced the same things. If they did, then it is fair to say that Dr. Jekyll is just as guilty as Mr. Hyde for committing the murders, because regardless of what he looked like or spoke like, he willingly and knowingly participated in the crimes.
References
Cohen, E. (2003). Hyding the Subject?: The Antinomies of Masculinity in the Strange Case of Dr. Jekyll and Mr. Hyde. Novel, 37(1/2), 181. Retrieved May 14, 2010, from http://proquest.umi.com/pqdweb?did=791925811&sid=1&Fmt=3&clientId=74379&RQT=309&VName=PQD
