MOSCOW, January 28 - RAPSI. Police plan to use a polygraph when interrogating witnesses in investigating the acid attack on Bolshoi Theater artistic director Sergei Filin, a spokesman of the Interior Ministry told RIA Novosti on Monday.

"The investigators will use a lie detector for the psychophysiological detection of any deception in this criminal case," the source said.

On January 17, an unidentified person threw what is believed to have beem sulfuric acid on Filin's face near his house in Moscow. Filin was rushed to a hospital with third degree burns to his face and eyes. He will have to undergo several plastic surgeries and a lengthy recovery period. He is expected to recover his vision.

A criminal case on Filin's attack was launched on charges of deliberate infliction of grave damage to health. The maximum punishment for this crime is eight years.

No suspects have yet been named in the case.