Here in Alabama we have a" best evidence rule" that states we can ask for only original documents. The federal rules of evidence 106 that says"we are entitled to the remainder of what ever is being introduced.Most all "BILL OF SALES" reference a "forward flow agreement",which contains everything. Most junk debt buyers dont wont to introduce this because it normally says there is not guarantee of anything being correct or accurate and you are buying as-is.,which would blow their case out of the water. Plus,this is just my opinion,if you see where they paid $100 for your $5000 debt isnt that unjust enrichment? Why would i pay more than what they expended? I have seen this work a few times.
All affidavits ,on face value,are "hearsay" because they happened out of court but they can be introduced into evidence if you dont object. Are you sure who wrote those affidavits have personal knowledge of your account?