Sematimba was born on Eros and worked as an inspector for Protogen until Eros's contract switched to CPM.
Sematimba and Miller coordinated a particular ugly case. A smuggler with cargo of designer euphorics had broken with his supplier. Three people on Ceres had been caught in the crossfire, and the smuggler had shipped out for Eros. The traditional competitiveness and insularity of the stations' respective security forces had almost let the perp slip away. Only Miller and Sematimba had been willing to coordinate outside the corporate channels.
When the crew of the Roci was involved in a firefight at a flophouse, Miller calls Semi to help them stay out of jail and show him the corpse of Julie Mao.