Answer: No. Every witness who testifies under oath in any proceeding is immune from civil liability for money damages, even for false testimony. This means that a witness under oath cannot be sued for damages by another person who may have suffered a loss as a result of that false testimony.
Witnesses testifying under oath are protected in this way so as to encourage all witnesses to come forward and testify freely. To function properly, our system of law requires sworn testimony; the idea behind granting immunity to witnesses testifying under oath is that without it, people may be afraid to testify, even truthfully, if they think they may be sued for doing so. Although the immunity granted to witnesses testifying under oath may lead to some people testifying falsely, that risk is considered outweighed by the need to encourage witnesses to testify without fear of civil liability and the risk that the threat of being sued would intimidate witnesses. So, a party to a civil lawsuit who loses because of false testimony cannot sue the lying witness for damages.
But, the lying witness cannot be confident that he can lie under oath without any penalty. A witness who lies under oath has committed perjury and could be charged with that crime. A perjury conviction carries a possible prison sentence and fine (which is a payment to the government). The court sentencing the perjurer can also order him to pay the victim (in this case, you) restitution. Restitution is money that a defendant must pay to the victim of his crime in order to try to compensate the victim for the harm caused. You may be entitled to restitution of money you lost as a result of losing the case due to your ex-business partner’s perjury.
For more information on perjury, see Perjury.
Also, if the witness lied about you when he was not under oath, for example, when talking to other people in your community, and you can show that the lies told in that setting caused you damage, you may be able to sue that lying witness. This would include lies that damaged your professional reputation or your business’s reputation. See a lawyer to find out if you have grounds for a lawsuit.