Popa….
“If we required people to claim that they didn’t do it, that would be requiring them to testify against themselves. Which is illegal under the constitution’
Unless the client pleads guilty the client is required to say they didn’t do it by pleading not guilty (it can be by reasons of insanity, etc.) That is not testifying, because the client is generally speaking through the mouth of his attorney, and neither the attorney or the client has been sworn in to give testimony as a witness at that point.
Non-attorneys often confuse pleading and opening statements with sworn witness testimony. They are far different and have different rules and protections. That is why jury instructions often include a warning that nothing said by the attorneys in opening statements should ever be considered as evidence during jury deliberations.
Your logic that a not-guilty plea is testimony against him/herself is not true. A plea of guilty is against the defendant, and 5th Amendment rights can’t compel self incrimination.