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..501a7423
--- /dev/null
+++ b/vetomint/src/misbehavior.rs
@@ -0,0 +1,131 @@
+use super::*;
+use state::*;
+
+use std::collections::HashMap;
+
+/// comment for check_double_proposal
+pub(crate) fn check_double_proposal(
+    state: &ConsensusState,
+    target_round: Round,
+) -> Vec<ConsensusResponse> {
+    let proposals: Vec<_> = state
+        .proposals
+        .iter()
+        .filter(|(_, proposal)| proposal.round == target_round)
+        .map(|(_, proposal)| proposal)
+        .collect();
+
+    if proposals.len() > 1 {
+        let byzantine_signer = proposals[0].proposer;
+        let (origin_proposal, new_proposal) = (proposals[0].proposal, proposals[1].proposal);
+
+        return vec![ConsensusResponse::ViolationReport {
+            violator: 0,
+            misbehavior: Misbehavior::DoubleProposal {
+                byzantine_node: byzantine_signer,
+                round: target_round,
+                proposals: (origin_proposal, new_proposal),
+            },
+        }];
+    }
+
+    Vec::new()
+}
+
+/// comment for check_double_prevote
+pub(crate) fn check_double_prevote(
+    state: &ConsensusState,
+    target_round: Round,
+) -> Vec<ConsensusResponse> {
+    let mut validators_map = HashMap::new();
+
+    for vote in state.prevotes.iter() {
+        let (count, origin_proposal) = validators_map
+            .entry(vote.signer)
+            .or_insert((0, vote.proposal));
+
+        *count += 1;
+
+        if *count == 2 {
+            let new_proposal = vote.proposal;
+            let byzantine_signer = vote.signer;
+
+            return vec![ConsensusResponse::ViolationReport {
+                violator: byzantine_signer,
+                misbehavior: Misbehavior::DoublePrevote {
+                    byzantine_node: byzantine_signer,
+                    round: target_round,
+                    proposals: (*origin_proposal, new_proposal),
+                },
+            }];
+        }
+    }
+
+    Vec::new()
+}
+
+/// comment for check_double_precommit
+pub(crate) fn check_double_precommit(
+    state: &ConsensusState,
+    target_round: Round,
+) -> Vec<ConsensusResponse> {
+    let mut validators_map = HashMap::new();
+
+    for vote in state.precommits.iter() {
+        let (count, origin_proposal) = validators_map
+            .entry(vote.signer)
+            .or_insert((0, vote.proposal));
+
+        *count += 1;
+
+        if *count == 2 {
+            let byzantine_signer = vote.signer;
+            let new_proposal = vote.proposal;
+
+            return vec![ConsensusResponse::ViolationReport {
+                violator: byzantine_signer,
+                misbehavior: Misbehavior::DoublePrecommit {
+                    byzantine_node: byzantine_signer,
+                    round: target_round,
+                    proposals: (*origin_proposal, new_proposal),
+                },
+            }];
+        }
+    }
+
+    Vec::new()
+}
+
+/// comment for check_invalid_proposal
+pub(crate) fn check_invalid_proposal(
+    byzantine_proposer: usize,
+    target_round: Round,
+    target_proposal: BlockIdentifier,
+) -> Vec<ConsensusResponse> {
+    return vec![ConsensusResponse::ViolationReport {
+        violator: byzantine_proposer,
+        misbehavior: Misbehavior::InvalidProposal {
+            byzantine_node: byzantine_proposer,
+            round: target_round,
+            proposal: target_proposal,
+        },
+    }];
+}
+
+/// comment for check_invalid_prevote
+pub(crate) fn check_invalid_prevote(
+    state: &ConsensusState,
+    target_round: Round,
+    target_proposal: BlockIdentifier,
+) -> Vec<ConsensusResponse> {
+    unimplemented!()
+}
+
+/// comment for check_invalid_precommit
+pub(crate) fn check_invalid_precommit(
+    state: &ConsensusState,
+    check_round: Round,
+    check_proposal: BlockIdentifier,
+) -> Vec<ConsensusResponse> {
+    unimplemented!()
+}
diff --git a/vetomint/src/progress.rs b/vetomint/src/progress.rs
index 24978407..7679b2ca 100644
--- a/vetomint/src/progress.rs
+++ b/vetomint/src/progress.rs
@@ -23,6 +23,10 @@ pub(crate) fn progress(
             round,
             favor,
         } => {
+            if valid == false {
+                // TODO: add possible invalid proposal logcis
+                return misbehavior::check_invalid_proposal(proposer, round, proposal);
+            }
             state.proposals.insert(
                 proposal,
                 Proposal {
@@ -46,6 +50,7 @@ pub(crate) fn progress(
                 state, round, proposal,
             ));
             response.extend(on_4f_non_nil_precommit(state, round, proposal));
+            response.extend(misbehavior::check_double_proposal(state, round));
             response
         }
         ConsensusEvent::SkipRound { round } => progress(
@@ -86,6 +91,7 @@ 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 +110,7 @@ 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 => {