A woman whose son was murdered during a shopping mall holdup says she will try to change a law that prevents a 14-year-old defendant from being tried as an adult. State law only allows judges to shift youngsters ages 16 and 17 from juvenile to adult court. Those younger than 16 must be handled in Juvenile Court. "This law is unfair," said Judy Luecke. "How can anyone hide behind an arbitrary age limit? They just picked the age out of a hat." Her son, Robert Luecke III, 23, was gunned down while shopping with his fiancee and his 13-year-old sister Dec. 3. Three youths, ages 14, 16 and 17 have been booked for investigation of murder. A hearing is scheduled Jan. 24 to determine whether the older boys should be tried in adult court, where they could face sentences of 25 years to life. The 14-year-old can only be held until he is 25. Luecke has launched a letter-writing campaign to persuade the Juvenile Court judge that the older boys should be moved to adult court.