The defendant was not credible; therefore, the jury voted to convict her.
I say this a lot, but I don't like the use of the semi-colon. To be honest, I rarely like the use of a semi-colon so the problem could be mine, not a problem with the sentence. However, I would say:
- The defendant was not credible so the jury voted to convict her.
- The defendant was not credible. As a result, the jury voted to convict her.
- The defendant was not credible. Therefore, the jury voted to convict her.
I also wonder about "voted to convict". It may be the AmE way, but in BrE, we would say "the jury found her guilty".
Edit: I have amended my third sentence because the original was nonsense.