Equivalence Relations Which Are Borel Somewhere

The following will be shown: Let I be a σ-ideal on a Polish space X so that the associated forcing of I + Δ^1_1 sets ordered by ⊆ is a proper forcing. Let E be a Σ^1_1 or a ∏^1_1 equivalence relation on X with all equivalence classes Δ^1_1. If for all z ∈_H(2^N0)+, z ♯ exists, then there exists an I + Δ^1_1 set C ⊆ X such that E ↾ C is a Δ^1_1 equivalence relation.