A method and related apparatus for confirming whether a kill laser successfully destroys an undesired population of cells includes introducing fluorescent dye into cells, exciting the cells with a detection laser or a light emitting diode to cause the cell to fluoresce for a first time, measuring the amount of fluorescence in the cells with a detector capable of emitting a detection pulse, classifying the cells via embedded processing as undesired or desired cells based on the amount of fluorescence, firing a kill beam with a kill laser at any undesired cells, measuring the amount of fluorescence in the cells a second time to determine whether a fluorescent event was generated from the kill beam striking the cells, and providing feedback to an operator of the kill laser as to whether any fluorescent events were generated from the kill beam striking the cells.