Des Moines homicide investigators rarely see an open-and-shut case like the one that literally walked in yesterday (Sunday).He apparently figured he’d be going to jail eventually, so Henry Clemons evidently decided he’d save officers the trouble. The 48-year-old Des Moines man walked into the Polk County Jail on Sunday afternoon and confessed he’d killed his girlfriend. Police say Clemons took them directly to the rural road near the airport where he’d dumped the body of Rogena Fisher, also 48 and from Des Moines. Officers say she’d been stabbed several times. Clemons is charged with murder, the 12th homicide in Des Moines this year.