CTL: If a potential client admits his guilt to a capital offense to any potential attorney he speaks with, no attorney can plead not guilty on his behalf?
Of course the lawyer can, and should. Pleading not guilty is not saying you didn’t do it; it’s just saying the government has to do its job in proving it.
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, and under halacha also.