diff --git a/state/execution.go b/state/execution.go
index 31f2662bf..d838531f8 100644
--- a/state/execution.go
+++ b/state/execution.go
@@ -309,7 +309,14 @@ func (s *State) validateBlock(b *types.Block) error {
 		}
 	}
 
-	// TODO: Validate evidence
+	for _, ev := range block.Evidence.Evidence {
+		if err := ev.VoteA.Verify(s.ChainID, ev.PubKey); err != nil {
+			return types.ErrEvidenceInvalid(ev, err)
+		}
+		if err := ev.VoteB.Verify(s.ChainID, ev.PubKey); err != nil {
+			return types.ErrEvidenceInvalid(ev, err)
+		}
+	}
 
 	return nil
 }
diff --git a/types/evidence.go b/types/evidence.go
index 6eb744277..5e2be9b50 100644
--- a/types/evidence.go
+++ b/types/evidence.go
@@ -7,6 +7,15 @@ import (
 	"github.com/tendermint/go-crypto"
 )
 
+type ErrEvidenceInvalid struct {
+	Evidence Evidence
+	Error    error
+}
+
+func (err *ErrEvidenceInvalid) Error() string {
+	return fmt.Sprintf("Invalid evidence: %v. Evidence: %v", err.Error, err.Evidence)
+}
+
 // Evidence represents any provable malicious activity by a validator
 type Evidence interface {
 	Verify() error
@@ -49,7 +58,9 @@ func (dve *DuplicateVoteEvidence) Verify() error {
 	}
 
 	// Signatures must be valid
-	// TODO
+	if !dve.PubKey.Verify(SignBytes(chainID, dve.VoteA), dve.VoteA.Signature) {
+		return ErrVoteInvalidSignature
+	}
 
 	return nil
 }
diff --git a/types/vote.go b/types/vote.go
index a34bf9d45..82adf0d11 100644
--- a/types/vote.go
+++ b/types/vote.go
@@ -101,3 +101,14 @@ func (vote *Vote) String() string {
 		cmn.Fingerprint(vote.BlockID.Hash), vote.Signature,
 		CanonicalTime(vote.Timestamp))
 }
+
+func (vote *Vote) Verify(chainID string, pubKey crypto.PubKey) error {
+	if !bytes.Equal(pubKey.Address(), v.ValidatorAddress) {
+		return ErrVoteInvalidValidatorAddress
+	}
+
+	if !pubKey.VerifyBytes(SignBytes(chainID, vote), vote.Signature) {
+		return ErrVoteInvalidSignature
+	}
+	return nil
+}
diff --git a/types/vote_set.go b/types/vote_set.go
index 5b802ceb8..3f8a96e3a 100644
--- a/types/vote_set.go
+++ b/types/vote_set.go
@@ -178,9 +178,8 @@ func (voteSet *VoteSet) addVote(vote *Vote) (added bool, err error) {
 	}
 
 	// Check signature.
-	if !val.PubKey.VerifyBytes(SignBytes(voteSet.chainID, vote), vote.Signature) {
-		// Bad signature.
-		return false, ErrVoteInvalidSignature
+	if err := vote.Verify(voteSet.chainID, val.PubKey); err != nil {
+		return false, err
 	}
 
 	// Add vote and get conflicting vote if any