> *...that person will die in the manner* [*prescribed*].

Non-finite clauses functioning as modifiers in noun phrase structure are quite common. Here, the past-participial clause "prescribed" modifies the noun "manner".

Such clauses are semantically similar to relative clauses: compare *that person will* *die in the manner that is prescribed*.

Past-participial modifiers are bare passives, as evident from the admissibility of a _by_ phrase.