Assuming you are meaning you have them initiate an action that you do not know will have the consequence of their death, I do not see how you could label it as murder since you are not intentionally killing them by this method.
If, however, you are suggesting you are not murdering them because you never know if gravity will decide to work or not, then you would have a pretty good idea they would be killed and thus would be an indirect murder.
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There is no shame in not knowing; the shame lies in not finding out