The plea of guilty was entered in connection with the death of her infant son. 26-year-old Crystal Martin of Joplin entered that plea to two counts of permitting child abuse. Her 18-month-old daughter, Destiny Willoughby, died in October of 2000. 26-year-old Jason Robbins, Martin`s boy friend, entered a guilty plea to second degree murder in the same case. He must serve at least 40 years for his part in the crime. Investigators believe Robbins threw the child towards the floor and hit her head on a stereo speaker. Martin was given a four-year sentence but will be given credit for a year she has already served. She must also pay a $500 fine and $250 to a crime victim`s compensation fund.