> Aztec.nr API reference, v6.0.0 (mainnet and testnet). Index: https://docs.aztec.network/aztec-nr-api/v6.0.0/llms.txt

# Function get_nullifier_membership_witness

Module: `noir_aztec::oracle::get_nullifier_membership_witness`

```rust
pub unconstrained fn get_nullifier_membership_witness(
    block_header: BlockHeader,
    nullifier: Field,
) -> (NullifierLeafPreimage, MembershipWitness<42>)
```

Returns a leaf preimage and membership witness for `nullifier` in the nullifier tree whose root is defined in `block_header`.

This is used to prove that a nullifier exists in the tree (inclusion proof).