Taney wrote the decision and expanded the case far beyond its original intent. All seven justices voting in the majority wrote their own decisions. One, Justice Wayne, said he concurred with the Taney decision entirely. One, Justice Campbell, concurred on the point of Scott being a slave. Four other justices wrote their own separate opinions and none went to the extent that Taney did.
“All seven justices voting in the majority wrote their own decisions.”
Still, you would have to say it was a 7-2 decision.