Former school teacher Katryna Martin has been sentenced to 20 years in prison for having a sexual relationship with a female student she had been tutoring in her home. Martin, 29, pleaded guilty Monday on charges of sexual battery, touching of a child for lustful purposes and two counts of exploitation for using her cell phone to set up meetings with the girl. Circuit Judge Roger Clark gave her a total of 20 years and suspended 13 years, leaving seven to serve, followed by five years of probation. Assistant District Attorney Joel Smith said Martin must serve the seven years day-for-day without eligibility for early release because of the nature of the crimes. She also must register as a sex offender the rest of her life after release from prison.