Complex sentence: The agency required its prior receipt of a 55-per-cent deposit required to finalize the appointment, which prosecutors speculate would ensure the agency received of its portion of the payment, since the agency believed "Samantha" was abusing drugs.
Split into simpler sentences: The agency required prior receipt of a 55-per-cent deposit to finalize the appointment. Prosecutors speculated the agency wanted to ensure it would receive its portion of the payment, since the agency believed "Samantha" was abusing drugs.