diff --git a/vetomint/src/lib.rs b/vetomint/src/lib.rs
index f1d89a41..ada62202 100644
--- a/vetomint/src/lib.rs
+++ b/vetomint/src/lib.rs
@@ -1,3 +1,4 @@
+mod misbehavior;
 mod progress;
 mod state;
 
diff --git a/vetomint/src/misbehavior.rs b/vetomint/src/misbehavior.rs
new file mode 100644
index 00000000..67bbc3ee
--- /dev/null
+++ b/vetomint/src/misbehavior.rs
@@ -0,0 +1,76 @@
+use super::*;
+use state::*;
+
+use std::collections::HashMap;
+
+/// Check whether there are double prevotes in target round
+pub(crate) fn check_double_prevote(
+    state: &ConsensusState,
+    target_round: Round,
+) -> Vec<ConsensusResponse> {
+    let mut validators_map = HashMap::new();
+    let prevotes_in_target_round: Vec<_> = state
+        .prevotes
+        .iter()
+        .filter(|vote| vote.round == target_round)
+        .collect();
+
+    for vote in prevotes_in_target_round.iter() {
+        let (count, origin_proposal) = validators_map
+            .entry(vote.signer)
+            .or_insert((0, vote.proposal));
+        *count += 1;
+
+        if *count == 2 {
+            let byzantine_validator = vote.signer;
+            let double_proposal = vote.proposal;
+
+            return vec![ConsensusResponse::ViolationReport {
+                violator: byzantine_validator,
+                misbehavior: Misbehavior::DoublePrevote {
+                    byzantine_node: byzantine_validator,
+                    round: target_round,
+                    proposals: (*origin_proposal, double_proposal),
+                },
+            }];
+        }
+    }
+
+    Vec::new()
+}
+
+/// Check whether there are double precommits in target round
+pub(crate) fn check_double_precommit(
+    state: &ConsensusState,
+    target_round: Round,
+) -> Vec<ConsensusResponse> {
+    let mut validators_map = HashMap::new();
+    let precommits_in_target_round: Vec<_> = state
+        .precommits
+        .iter()
+        .filter(|vote| vote.round == target_round)
+        .collect();
+
+    for vote in precommits_in_target_round.iter() {
+        let (count, origin_proposal) = validators_map
+            .entry(vote.signer)
+            .or_insert((0, vote.proposal));
+        *count += 1;
+
+        if *count == 2 {
+            let byzantine_validator = vote.signer;
+            let double_proposal = vote.proposal;
+
+            return vec![ConsensusResponse::ViolationReport {
+                violator: byzantine_validator,
+                misbehavior: Misbehavior::DoublePrecommit {
+                    byzantine_node: byzantine_validator,
+                    round: target_round,
+                    proposals: (*origin_proposal, double_proposal),
+                },
+            }];
+        }
+    }
+
+    Vec::new()
+}
diff --git a/vetomint/src/progress.rs b/vetomint/src/progress.rs
index 24978407..e5ff8a9e 100644
--- a/vetomint/src/progress.rs
+++ b/vetomint/src/progress.rs
@@ -86,6 +86,7 @@ pub(crate) fn progress(
                 response.extend(on_4f_nil_prevote(state, round));
             }
             response.extend(on_5f_prevote(state, round, proposal));
+            response.extend(misbehavior::check_double_prevote(state, round));
             response
         }
         ConsensusEvent::Precommit {
@@ -104,6 +105,7 @@ pub(crate) fn progress(
             if let Some(proposal) = proposal {
                 response.extend(on_4f_non_nil_precommit(state, round, proposal));
             }
+            response.extend(misbehavior::check_double_precommit(state, round));
             response
         }
         ConsensusEvent::Timer => {