There are many branches of forensic science. The one most likely to appeal to little boys would probably be forensic entomology. Forensic entomology is the study of insects as they relate to solving crime. It can be used to poke holes in motives, find the origin of drugs, or most commonly, determine the time of death. 

     Let's say a man was being investigated in the death of a woman whose body was found by a lake. He claimed never to have been anywhere near a lake during the time period in question. Insects particular to the area in question found in the grill of his truck can refute his testimony. Based on their stage of development it can be determined when exactly they got there as well.
Marijuana is often imported into America from places like Mexico. The insect content in seized marijuana can often pinpoint the place it originated from. This in turn can help lead to the apprehension of the ones responsible for it.
While these are possible uses of forensic entomology, the most common one is determining a corpse's time of death. Insects come upon a body in stages. First are the flies, then other insects follow in stages. The time of death can be determined by the type of insects found on the body and the stage of development it's in. For example, if fly eggs are found on the body, it's a relatively new corpse. The eggs laid by the insects that come later on are found, the corpse has been there significantly longer. Forensic entomologists have charts showing the correlation between type of insect, stage of insect and time of death.

     To make these charts, controlled studies need to be performed. Pigs make good models of human bodies with their hairless skins. Sheep mimic corpses with clothes on relatively well. These trials allowed scientists to factor in the many variables associated with decomposition, mainly those that affected temperature. These include whether or not the corpse was clothed, whether it was on land or in the water and the temperature changes caused by masses of insects themselves.

     Based on these trials, scientists are able to look at a corpse and determine when it died. This would not have been possible without the unwitting help of those creepy crawly things that little boys played with when they were too young to understand just how important they were.