Building a strong record of the infestation
You prove a bed bug infestation with documentation: dated photos of live bugs, blood spots, shed skins, and bites; written reports to your landlord; any pest-control or inspection records; and receipts for discarded or replaced belongings.
Build the record over time. Photograph bugs in the seams of the mattress and furniture, dark droppings, and bites as they appear on your skin. Save every text and email with your landlord, since these show what the landlord knew and when. Keep any exterminator reports, which can confirm the infestation and the treatment attempts.
Medical records for bites or reactions, and receipts for replaced mattresses or furniture, help show the full impact. You do not need a laboratory to have proof; a clear, dated record usually tells the story. A free review can help you understand which evidence matters most in your situation.
This is general information about California tenant rights, not legal advice. Every situation is different.