AuthorizeNET DPM relayresponse URL won't redirect

[spastic]

I am coding to the AuthorizeNet DPM API. 

The issue is I have is I am trying to put security into the DPM relay response script on my server for security reasons to do a checksum on the hash and other information coming back from AuthorizeNet to verify the response is legit.  My program does a response.redirect to an error page if it is not legit. 

I'm not sure how, but the AuthorizeNet is simply "ignoring" my redirect from the server to the error page and only showing the page as if it is authentic when it has clearly failed several tests.  Any ideas on "how" it is doing this and how to make it stop?

[RaynorC1emen7]

When it redirects, authorizenet throws this text into my page for some reason.

response.redirect or javascript redirect?

I am able to test with and without authorizeNet using a flag, so this is 100% an authorizenet artifact.

what flag?

What kind of encoding Is that TM in?  Can't you just use regular text and make the size smaller?