case?

It is known that two rules are related to assigning case to NPs.

1.case filter
Every overt NP must be assigned case by such appropriate case assignors as a preposition, the finite tense, complementizer for, and a transitive verb.

2. adjacency requirement
For the case assignor to assign case to NPs, the two must be adjacent.

Then, what about the following sentence?
He knew John to be the best student.

As my thinking,
He is assigned case by the finite tensev(past-tense).
John is given case by the transitive verb (know)
the best student is allocated case by John (case-
sharing)

Then, the best student apparently bears the objective case as John does.
But it is incongruous with the syntactic feature of each word, I think.
John is the subject of to-infitive clause and
the best student is the subject-complement NP of to-infinitive clause.
Also, it is unlikely to think of the best student as bearing objective case.

How do I view this mismatch between case and syntactic function?