The separability problem is a concept from the field of social choice theory that describes the situation where two or more issues up for vote on a ballot either are, or are perceived as, related.
The separability problem commonly manifests itself most intensely in referendums and in voting on multiple charges before juries or panels of judges, where simultaneous voting is employed.
The voters have no information on the outcome of related issues, so they simply cast their first preference votes.
The solution to the separability problem for referendums would be set-wise voting, where the voter can express preferences for outcomes of related issues, as this process needs to be done at a particular time.
The drawback to sequential voting in this case would be that there is no means to guarantee that a juror would actually change a successive vote based on a prior verdict.