(a) In any case where a member who has been a contributing member for at least 10 years dies prior to retirement from any cause other than those specified in §20-18-25 of this code, and not due to vicious habits, intemperance, or willful misconduct on his or her part, the fund shall pay annually in equal monthly installments to the surviving spouse during his or her lifetime, a sum equal to the greater of:

1. (i) One half of the annual compensation received by the deceased member during the last 12 full months of contributory service; or (ii) if the member dies after meeting normal retirement age requirements, the monthly amount which the spouse would have received had the member retired the day before his or her death, elected a 100 percent joint and survivor annuity with the spouse as the joint annuitant, and then died.

(b) In any case where a retirant who had been a contributing member for at least 10 years, had not obtained the age of 60, and was receiving benefits pursuant to §20-18-22 of this code dies and leaves a surviving spouse, the fund shall pay annually in equal monthly installments to the surviving spouse during his or her lifetime a sum equal to the greater of:

1. (i) One half of the annual compensation received by the deceased member during the last 12 full months of contributory service; or (ii) if the retirant dies after meeting normal retirement age requirements, the monthly amount which the spouse would have received had the member retired the day before his or her death, elected a 100 percent joint and survivor annuity with the spouse as the joint annuitant, and then died.