Television shows such as CSI (and the subsequent CSI Miami and CSI New York), NCIS, and Cold Case Files have made crime scenes and crime investigations the new murder mystery parties. They are a great deal of fun when properly planned and well executed but leave a lot of room for failure if poorly planned or inflexible. If you are considering a party such as this, a great party for teens and adults alike be sure that you either have an actual mystery to solve as the evening progresses or that you simply use the theme as a backdrop. There is no real right or wrong way to do a birthday party but if you want to throw the party that everyone will be talking about you'll need to create a crime for the scene you're investigating and leave clues all around to help with the investigation.
Decorating your crime scene party can be a lot of fun with crime scene tape and chalk outlines on the floor. Be sure to make them realistic in size by having someone actually lay down for you to draw the outline. You can leave fake footprints, fingerprints, and clue cards throughout the room (not too well hidden unless you want people snooping). You can even enlist plenty of help when leaving the clues and decorating because of the novelty of this sort of party. You do not have to limit the festivities to one room and you can, if you are feeling truly adventurous, have a different case going on in different rooms and have the kids draw numbers for teams and race to solve the crime first.
You might also do well to set up a lab, complete with microscope and tables dedicated to sorting out the evidence and make notes for the shocking conclusion of the crimes in question. Of course you will want to make the crimes simple and solvable by leaving clues that the kids will have no trouble finding or deciphering without making it too easy. Use your favorite episode for inspiration if you must and throw in a red herring or two to keep things fun. Young and old alike, the kids will have a good time arguing over the clues and trying to determine who really committed the crimes (and of course making up their assumptions and stories as to why the crimes occurred in the first place).
For food you can have an actual CSI cake or go with cookies that are shaped like footprints or thumb print cookies for an excellent play on words. Of course by the time kids are old enough to enjoy a party such as this they probably would be happy with good food rather than themed food and pizza, sloppy Joes, finger foods, chips and dips, and cookies and cake will make an excellent food addition to the party without needing to fit in with any one theme. Be sure to have plenty of pop and bottled water on hand though because crime solving is thirsty work.
In real life it is best to leave the jobs of solving crimes up to the men and women who were trained to do so. In the world of birthday parties however, crime solving and crime scene investigating reign supreme as the next great thing in birthday party ideas.