Transit officials said there were no known witnesses to the incident.

Although there are no known witnesses to the killings, many local residents allege that they were carried out by members of the security forces.

A known witness, clearly going to be testifying, a subordinate employee who is called in and coached.

Since there are no known witnesses to the transaction, the case is all but closed.

Borgia's only attendant was also slain, so there were no known witnesses.

The police said there were no known witnesses to the struggle.

And the only known witnesses to the crime are the white boy's white friends.

And it would help us if maybe we could talk to the only known witness.

With both men dead, and with no known witnesses, the specific motive for the attack remains unknown.

External evidence is evidence of each physical witness, its date, source, and relationship to other known witnesses.