how far back does the court want to see bank statements in a chapter 7

The court doesn't want to see bank statements.  The Trustee in your case may request them though.  Every Trustee has different requirements, so there's no way to say what would happen in your specific case.  I've seen them request as far back as 2 years, but usually it's 6 months if there's an issue.  The US Trustee's office can also request documents to verify information put on the means test and other forms.  And your case can be audited and the auditors can request bank statements, but that is typically 6 months worth.