Abstract: A mechanical lysis method includes (a) spinning a mixing head at a spin rate in a liquid sample, containing cells and beads, such that the mixing head cooperates with the beads to lyse the cells, wherein the spin rate exceeds a threshold rate associated with a predefined lysis efficiency, and (b) preventing the mixing head from spinning if the spin rate cannot be maintained above the threshold rate. A lysis apparatus includes (a) a receptacle for holding a container containing a liquid sample with cells and beads, (b) a mixing head configured to spin in the liquid sample, (c) a motor configured to spin the mixing head such that the mixing head cooperates with the beads to lyse the cells, and (d) a switch configured to prevent spinning of the mixing head at a spin rate lower than a threshold rate associated with a predefined lysis efficiency.