Final answer:
Using forensic entomology, the date when blow flies first deposited eggs on a cadaver can be estimated by analyzing the development stage of the maggots recovered and comparing it to known growth rates under specific conditions, establishing the postmortem interval (PMI).
Step-by-step explanation:
The earliest possible date when the first adult blow flies deposited eggs on the victim's body can be estimated by a forensic entomologist, who will examine the stages and types of maggots present on the cadaver. Because blow flies are attracted to decaying flesh to lay their eggs, the developmental stage of the maggots can be used to compare against known growth rates for these insects under specific environmental conditions. This process provides crucial information to help determine the postmortem interval (PMI), which is the time that has elapsed since death.