A lone witness is not sufficient to establish any wrongdoing or sin against a man, regardless of what offense he may have committed. A matter must be established by the testimony of two or three witnesses.

Matthew 18:16
But if he will not listen, take one or two others along, so that 'every matter may be established by the testimony of two or three witnesses.'

Matthew 26:60
But they did not find any, though many false witnesses came forward. Finally two came forward

John 7:51
"Does our law convict a man without first hearing from him to determine what he has done?"

John 8:17
Even in your own Law it is written that the testimony of two men is valid.

2 Corinthians 13:1
This is the third time I am coming to you. "Every matter must be established by the testimony of two or three witnesses."

1 Timothy 5:19
Do not entertain an accusation against an elder, except on the testimony of two or three witnesses.

Hebrews 10:28
Anyone who rejected the law of Moses died without mercy on the testimony of two or three witnesses.

Numbers 35:30
If anyone kills a person, the murderer is to be put to death on the testimony of the witnesses. But no one is to be put to death based on the testimony of a lone witness.

Deuteronomy 17:6
On the testimony of two or three witnesses a man shall be put to death, but he shall not be executed on the testimony of a lone witness.

One witness shall not rise up against a man for any iniquity, or for any sin, in any sin that he sins: at the mouth of two witnesses, or at the mouth of three witnesses, shall the matter be established.