diff --git a/judge_message b/judge_message
index 3ab99a2..9e5bc09 100755
--- a/judge_message
+++ b/judge_message
@@ -32,7 +32,7 @@ def add_message(msg):
                     msg.get_payload(decode=True)
                         .decode(charset, errors='replace'))
 
-def extract_features(msgid, verbose):
+def extract_features(msgid, verbose, used_evidence):
     db = psycopg2.connect("dbname=bayes")
     csr = db.cursor(cursor_factory=ppe.DictCursor)
     csr.execute(
@@ -87,9 +87,10 @@ def extract_features(msgid, verbose):
     for i in interesting_evidence:
         if verbose:
             print("#", i["spam_prob"], i["type"], i["length"], i["feature"], sep="\t")
-        csr.execute(
-            "insert into used_evidence(message, spam_prob, type, length, feature) values(%s, %s, %s, %s, %s)",
-            (msg_pk, i["spam_prob"], i["type"], i["length"], i["feature"]))
+        if used_evidence:
+            csr.execute(
+                "insert into used_evidence(message, spam_prob, type, length, feature) values(%s, %s, %s, %s, %s)",
+                (msg_pk, i["spam_prob"], i["type"], i["length"], i["feature"]))
         p1 *= i["spam_prob"]
         p2 *= 1 - i["spam_prob"]
     p = p1 / (p1 + p2)
@@ -100,6 +101,7 @@ def extract_features(msgid, verbose):
 def main():
     ap = argparse.ArgumentParser()
     ap.add_argument('--verbose', action='store_true')
+    ap.add_argument('--no-used-evidence', action='store_false', dest='used_evidence')
     ap.add_argument('file', nargs='?')
     args = ap.parse_args()
     if args.file:
@@ -109,7 +111,7 @@ def main():
     parser = email.parser.BytesParser(policy=email.policy.default)
     msg = parser.parse(fh)
     add_message(msg)
-    p = extract_features(msg["Message-Id"], args.verbose)
+    p = extract_features(msg["Message-Id"], args.verbose, args.used_evidence)
     print(p, "spam" if p > 0.5 else "ham")
 
 main()