Answer
The source of cryptocurrency funds can be verified if their trail is traceable. It is important to show not just the current balance, but the full chain: what funds were used to purchase the asset, where it was stored, how it was transferred, where it was sold, and where the fiat funds were received.
For this purpose, exchange statements, purchase receipts, wallet addresses, transaction IDs, and transaction settlement records are useful. A wallet screenshot alone is weak evidence because it does not explain the asset's origin or the subsequent receipt of funds.
The larger the amount, the more detailed the reconstruction of the transaction trail should be. A sale through an identifiable platform, with proceeds withdrawn to a personal account belonging to the same owner, appears more transparent than a set of scattered transfers from strangers with no explainable connection to the original capital.