Short answer: Yes. I've heard testimony from Christians who have spoken of this - and they said that even though they were backslidden they continued to prayer in the Spirit, in an unknown language. They have said that this was a major part of their being able to get through their trials, - knowing that the Holy Spirit was giving them the perfect prayers to speak.In that case can a backslidden man/woman speak in tongues?
1 Corinthians 14:4 He that speaketh in an unknown tongue edifieth himself . . . . .
In writing to the church at Corinth, Paul encouraged them to continue the practice of speaking with other tongues in their worship of God and in their prayer lives as a means of spiritual edification or building up. "For he that speaketh in an unknown tongue speaketh not unto men, but unto God: for no man understandeth him; howbeit in the spirit he speaketh mysteries" (1 Cor. 14:2).
Paul is saying here that God has given to the church a divine, supernatural means of communication with Himself. In the 14th verse of this chapter Paul stated, "For if I pray in an unknown tongue, my spirit prayeth, but my understanding is unfruitful." Notice that he said, "my spirit prayeth." The Amplified translation adds, "My spirit (by the Holy Spirit within me) prays." God is Spirit. When we pray in tongues, our spirit is in direct contact with God, who is Spirit. We are talking to Him.