diff --git a/src/common-crypto/CryptoBackend.ts b/src/common-crypto/CryptoBackend.ts
index f13777fb9..5758858ad 100644
--- a/src/common-crypto/CryptoBackend.ts
+++ b/src/common-crypto/CryptoBackend.ts
@@ -213,11 +213,6 @@ export interface EventDecryptionResult {
      * ed25519 key claimed by the sender of this event. See {@link MatrixEvent#getClaimedEd25519Key}.
      */
     claimedEd25519Key?: string;
-    /**
-     * Whether the keys for this event have been received via an unauthenticated source (eg via key forwards, or
-     * restored from backup)
-     */
-    untrusted?: boolean;
 }
 
 /**
diff --git a/src/models/event.ts b/src/models/event.ts
index ec6672c6f..abdda8412 100644
--- a/src/models/event.ts
+++ b/src/models/event.ts
@@ -185,8 +185,7 @@ export interface IDecryptOptions {
     isRetry?: boolean;
 
     /**
-     * Whether the message should be re-decrypted if it was previously successfully decrypted with an untrusted key.
-     * Defaults to `false`.
+     * @deprecated does nothing
      */
     forceRedecryptIfUntrusted?: boolean;
 }
@@ -284,10 +283,6 @@ export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, Mat
      */
     private claimedEd25519Key: string | null = null;
 
-    /* where the decryption key is untrusted
-     */
-    private untrusted: boolean | null = null;
-
     /* if we have a process decrypting this event, a Promise which resolves
      * when it is finished. Normally null.
      */
@@ -887,8 +882,7 @@ export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, Mat
         }
 
         const alreadyDecrypted = this.clearEvent && !this.isDecryptionFailure();
-        const forceRedecrypt = options.forceRedecryptIfUntrusted && this.isKeySourceUntrusted();
-        if (alreadyDecrypted && !forceRedecrypt) {
+        if (alreadyDecrypted) {
             // we may want to just ignore this? let's start with rejecting it.
             throw new Error("Attempt to decrypt event which has already been decrypted");
         }
@@ -1022,7 +1016,6 @@ export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, Mat
         this.clearEvent = decryptionResult.clearEvent;
         this.senderCurve25519Key = decryptionResult.senderCurve25519Key ?? null;
         this.claimedEd25519Key = decryptionResult.claimedEd25519Key ?? null;
-        this.untrusted = decryptionResult.untrusted || false;
         this.invalidateExtensibleEvent();
     }
 
@@ -1041,7 +1034,6 @@ export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, Mat
         };
         this.senderCurve25519Key = null;
         this.claimedEd25519Key = null;
-        this.untrusted = false;
         this.invalidateExtensibleEvent();
     }
 
@@ -1126,11 +1118,10 @@ export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, Mat
     }
 
     /**
-     * Whether the decryption key was obtained from an untrusted source. If so,
-     * we cannot verify the authenticity of the message.
+     * @deprecated always returns false
      */
-    public isKeySourceUntrusted(): boolean | undefined {
-        return !!this.untrusted;
+    public isKeySourceUntrusted(): false {
+        return false;
     }
 
     public getUnsigned(): IUnsigned {
diff --git a/src/testing.ts b/src/testing.ts
index e929f551a..a8a6b5795 100644
--- a/src/testing.ts
+++ b/src/testing.ts
@@ -180,7 +180,6 @@ export async function decryptExistingEvent(
             content: opts.plainContent,
         },
         senderCurve25519Key: "",
-        untrusted: false,
     };
 
     const mockCrypto = {