Because you can't provide corroboration or evidence to support it.

Such conversations, especially between Serbian commanders, could provide corroboration for witness testimony.

As though providing corroboration of his thoughts, weapons fire suddenly battered the door through which Kirk had entered the lab.

But the Vista videotape would provide powerful corroboration of the drug dealers' testimony.

My experiment, instead of refuting Levine's work, only provides independent corroboration.

As an eyewitness to some of the events, Blackard provides especially strong corroboration.

Human excrement found in the cargo hold also provided corroboration that other stowaways had originally been aboard.

The report did not provide specific corroboration for the assertion.

"Give me some background about him," I said, "and tell me how his testimony provides corroboration concerning Jesus."

The detail provides credibility and corroboration to Ms. Lewinsky's testimony.