In all capital cases, other than those of homicide, when the verdict is "guilty," with a recommendation for mercy, it shall be legal and shall mean imprisonment for life. When the verdict is "guilty," without a recommendation for mercy, it shall be legal and shall mean that the convicted person shall be sentenced to death. When it is shown that a person convicted of a capital offense without a recommendation for mercy had not reached his seventeenth birthday at the time of the commission of the offense, the punishment of such person shall not be death but shall be imprisonment for life.