Complex sentence: Doctors in the hospital suspected at the time he had been poisoned with an organophosphate pesticide, but the cause of death was pinned down only after cult members arrested for the subway attack confessed to the killing.
Split into simpler sentences: Doctors in the hospital suspected at the time he had been poisoned with an organophosphate pesticide. But the cause of death was pinned down only after cult members arrested for the subway attack confessed to the killing.