"The Supreme Court had held that the testimony of the defendant, unshaken under cross-examination, is to be believed."
Is that true?
The key is credibility. Simply taking the stand and saying "I didn't do it" probably won't cut it. You'll need to provide a clear explanation of what took place. If your version of events is considered to be as credible as the officers, then it creates reasonable doubt. The Court can still believe the officer, but no more so then the defendant.
As with all things HTA, your success with this tactic will vary depending on the jurisdiction and J.P.