diff --git a/eth2/types/src/beacon_state/builder.rs b/eth2/types/src/beacon_state/builder.rs
index f6d7b3900..372f0d43d 100644
--- a/eth2/types/src/beacon_state/builder.rs
+++ b/eth2/types/src/beacon_state/builder.rs
@@ -1,24 +1,14 @@
 use super::BeaconStateError;
+use crate::validator_registry::get_active_validator_indices;
 use crate::*;
-use crate::{validator_registry::get_active_validator_indices, *};
-use bls::create_proof_of_possession;
 use rayon::prelude::*;
 use ssz::TreeHash;
 
-/// Builds a `BeaconState` for use in testing or benchmarking.
+/// Builds a `BeaconState` for use in production.
 ///
-/// Building the `BeaconState` is a three step processes:
+/// This struct should not be modified for use in testing scenarios. Use `TestingBeaconStateBuilder` for that purpose.
 ///
-/// 1. Create a new `BeaconStateBuilder`.
-/// 2. Call `Self::build()` or `Self::build_fast()` generate a  `BeaconState`.
-/// 3. (Optional) Use builder functions to modify the `BeaconState`.
-/// 4. Call `Self::cloned_state()` to obtain a `BeaconState` cloned from this struct.
-///
-/// Step (2) happens prior to step (3) because some functionality requires an existing
-/// `BeaconState`.
-///
-/// Step (4) produces a clone of the BeaconState and doesn't consume the `BeaconStateBuilder` to
-/// allow access to `self.keypairs` and `self.spec`.
+/// This struct should remain safe and sensible for production usage.
 pub struct BeaconStateBuilder {
     pub state: BeaconState,
 }
@@ -105,139 +95,4 @@ impl BeaconStateBuilder {
 
         Ok(self.state)
     }
-
-    /*
-    /// Sets the `BeaconState` to be in the last slot of the given epoch.
-    ///
-    /// Sets all justification/finalization parameters to be be as "perfect" as possible (i.e.,
-    /// highest justified and finalized slots, full justification bitfield, etc).
-    pub fn teleport_to_end_of_epoch(&mut self, epoch: Epoch, spec: &ChainSpec) {
-        let state = &mut self.state;
-
-        let slot = epoch.end_slot(spec.slots_per_epoch);
-
-        state.slot = slot;
-        state.validator_registry_update_epoch = epoch - 1;
-
-        state.previous_shuffling_epoch = epoch - 1;
-        state.current_shuffling_epoch = epoch;
-
-        state.previous_shuffling_seed = Hash256::from_low_u64_le(0);
-        state.current_shuffling_seed = Hash256::from_low_u64_le(1);
-
-        state.previous_justified_epoch = epoch - 2;
-        state.justified_epoch = epoch - 1;
-        state.justification_bitfield = u64::max_value();
-        state.finalized_epoch = epoch - 1;
-    }
-
-    /// Creates a full set of attestations for the `BeaconState`. Each attestation has full
-    /// participation from its committee and references the expected beacon_block hashes.
-    ///
-    /// These attestations should be fully conducive to justification and finalization.
-    pub fn insert_attestations(&mut self) {
-        let state = &mut self.state;
-
-        state
-            .build_epoch_cache(RelativeEpoch::Previous, &self.spec)
-            .unwrap();
-        state
-            .build_epoch_cache(RelativeEpoch::Current, &self.spec)
-            .unwrap();
-
-        let current_epoch = state.current_epoch(&self.spec);
-        let previous_epoch = state.previous_epoch(&self.spec);
-        let current_epoch_depth =
-            (state.slot - current_epoch.end_slot(self.spec.slots_per_epoch)).as_usize();
-
-        let previous_epoch_slots = previous_epoch.slot_iter(self.spec.slots_per_epoch);
-        let current_epoch_slots = current_epoch
-            .slot_iter(self.spec.slots_per_epoch)
-            .take(current_epoch_depth);
-
-        for slot in previous_epoch_slots.chain(current_epoch_slots) {
-            let committees = state
-                .get_crosslink_committees_at_slot(slot, &self.spec)
-                .unwrap()
-                .clone();
-
-            for (committee, shard) in committees {
-                state
-                    .latest_attestations
-                    .push(committee_to_pending_attestation(
-                        state, &committee, shard, slot, &self.spec,
-                    ))
-            }
-        }
-    }
-
-    /// Returns a cloned `BeaconState`.
-    pub fn cloned_state(&self) -> BeaconState {
-        self.state.as_ref().expect("Genesis required").clone()
-    }
-    */
 }
-
-/*
-/// Builds a valid PendingAttestation with full participation for some committee.
-fn committee_to_pending_attestation(
-    state: &BeaconState,
-    committee: &[usize],
-    shard: u64,
-    slot: Slot,
-    spec: &ChainSpec,
-) -> PendingAttestation {
-    let current_epoch = state.current_epoch(spec);
-    let previous_epoch = state.previous_epoch(spec);
-
-    let mut aggregation_bitfield = Bitfield::new();
-    let mut custody_bitfield = Bitfield::new();
-
-    for (i, _) in committee.iter().enumerate() {
-        aggregation_bitfield.set(i, true);
-        custody_bitfield.set(i, true);
-    }
-
-    let is_previous_epoch =
-        state.slot.epoch(spec.slots_per_epoch) != slot.epoch(spec.slots_per_epoch);
-
-    let justified_epoch = if is_previous_epoch {
-        state.previous_justified_epoch
-    } else {
-        state.justified_epoch
-    };
-
-    let epoch_boundary_root = if is_previous_epoch {
-        *state
-            .get_block_root(previous_epoch.start_slot(spec.slots_per_epoch), spec)
-            .unwrap()
-    } else {
-        *state
-            .get_block_root(current_epoch.start_slot(spec.slots_per_epoch), spec)
-            .unwrap()
-    };
-
-    let justified_block_root = *state
-        .get_block_root(justified_epoch.start_slot(spec.slots_per_epoch), &spec)
-        .unwrap();
-
-    PendingAttestation {
-        aggregation_bitfield,
-        data: AttestationData {
-            slot,
-            shard,
-            beacon_block_root: *state.get_block_root(slot, spec).unwrap(),
-            epoch_boundary_root,
-            crosslink_data_root: Hash256::zero(),
-            latest_crosslink: Crosslink {
-                epoch: slot.epoch(spec.slots_per_epoch),
-                crosslink_data_root: Hash256::zero(),
-            },
-            justified_epoch,
-            justified_block_root,
-        },
-        custody_bitfield,
-        inclusion_slot: slot,
-    }
-}
-*/