Witness is one of those interesting words when defined in English. It can mean any of the following:
(1) A person who sees an event, typically a crime or accident, take place. (2) Evidence; proof
(1) See (an event, typically a crime or accident) take place. (2) Give or serve as evidence of; testify to
Some other words we see that mean the same thing as witness include, bystander, observer, spectator and testimony  (or testifier). Being a false witness is equivalent to being a liar. In the Bible we see examples of what it means to be a true and/or false witness. Here is what the Bible says about being a witness.
Eyewitnesses in the Early Church
Luke 1:1–4 FORASMUCH as many have taken in hand to set forth in order a declaration of those things which are most surely believed among us, Even as they delivered them unto us, which from the beginning were eyewitnesses, and ministers of the word; It seemed good to me also, having had perfect understanding of all things from the very first, to write unto thee in order, most excellent Theophilus, That thou mightest know the certainty of those things, wherein thou hast been instructed.
Luke 24:46–48 And said unto them, Thus it is written, and thus it behoved Christ to suffer, and to rise from the dead the third day: And that repentance and remission of sins should be preached in his name among all nations, beginning at Jerusalem. And ye are witnesses of these things.
Acts 1:22 Beginning from the baptism of John, unto that same day that he was taken up from us, must one be ordained to be a witness with us of his resurrection.
Acts 5:32 And we are his witnesses of these things; and so is also the Holy Ghost, whom God hath given to them that obey him.
Acts 10:39 And we are witnesses of all things which he did both in the land of the Jews, and in Jerusalem; whom they slew and hanged on a tree:
Acts 13:31 And he was seen many days of them which came up with him from Galilee to Jerusalem, who are his witnesses unto the people.
1 Peter 5:1 The elders which are among you I exhort, who am also an elder, and a witness of the sufferings of Christ, and also a partaker of the glory that shall be revealed:
2 Peter 1:16 For we have not followed cunningly devised fables, when we made known unto you the power and coming of our Lord Jesus Christ, but were eyewitnesses of his majesty.
Caution About Bearing False Witness
Exodus 20:16 Thou shalt not bear false witness against thy neighbour.
Exodus 23:1 Thou shalt not raise a false report: put not thine hand with the wicked to be an unrighteous witness.
Proverbs 12:17 He that speaketh truth sheweth forth righteousness: But a false witness deceit.
Proverbs 19:9 A false witness shall not be unpunished, And he that speaketh lies shall perish.
Proverbs 24:28 Be not a witness against thy neighbour without cause; And deceive not with thy lips.
Proverbs 25:18 A man that beareth false witness against his neighbour Is a maul, and a sword, and a sharp arrow.
Matthew 19:18 He saith unto him, Which? Jesus said, Thou shalt do no murder, Thou shalt not commit adultery, Thou shalt not steal, Thou shalt not bear false witness
Examples of False Witness
Matthew 28:12–15 And when they were assembled with the elders, and had taken counsel, they gave large money unto the soldiers, Saying, Say ye, His disciples came by night, and stole him away while we slept. And if this come to the governor’s ears, we will persuade him, and secure you. So they took the money, and did as they were taught: and this saying is commonly reported among the Jews until this day.
Mark 14:55–56 And the chief priests and all the council sought for witness against Jesus to put him to death; and found none. For many bare false witness against him, but their witness agreed not together.
Acts 6:11 Then they suborned men, which said, We have heard him speak blasphemous words against Moses, and against God.
Acts 17:6–7 And when they found them not, they drew Jason and certain brethren unto the rulers of the city, crying, These that have turned the world upside down are come hither also; Whom Jason hath received: and these all do contrary to the decrees of Caesar, saying that there is another king, one Jesus.
Acts 25:7 And when he was come, the Jews which came down from Jerusalem stood round about, and laid many and grievous complaints against Paul, which they could not prove.
We should be always looking for opportunities to give a true testimony of things that happen. Sometimes it is to help in the process of justice that we are a good and true witness. Sometimes it is to give our own personal testimony of how we came to know Jesus . Even so, many are tempted to give false witness against others. For this reason, the Bible also speaks of the need to have two or three witnesses in the matter (Deuteronomy 17:6; 1 Timothy 5:19, Hebrews 10:28). Sometimes we just need more than one witness to get to the truth of the matter.
More for you to read: You Shall Not Bear False Witness 
Resource – Scripture quotations are from The Holy Bible, King James Version.