Yes, but you do not have to prove that you haven’t copied the original; you have to prove you didn’t infringe copyright. For that there are other possible defenses, for example:
- fair use
- claiming the copied part doesn’t require creativity
- arguing that the copied code was written by AI (there’s jurisdiction that says AI-generated art can’t be copyrighted (https://www.theverge.com/2023/8/19/23838458/ai-generated-art...). It’s not impossible judges will make similar judgments for AI-generated programs)