If you watch detective and police shows, you’ll have some idea on how fingerprints are collected. It seems easy enough if you have the right tools. Here’s a basic idea on how it’s done.
- Prepare your tools. You will need the appropriate dusting powder to be able to lift a fingerprint sample from a given surface. The type and color of the surface determines what type or color powder you will need. For example, on light colored surfaces, a dark carbon powder is used. For dark surfaces, a light aluminum power is a better option. If you’re using powders, you’ll need a small dusting brush and some scotch tape. Have clean white index cards on standby, a pen and fresh ziplock bags to store your specimen.
- Wear latex gloves. When you’re handling fingerprint samples, it’s crucial you don’t contaminate the sample with your own prints.
- Take out your digital camera and start taking pictures of the crime scene. Take pictures of the area where you will get the prints. You will also need to take pictures of the surface where you find the prints after you have put some dusting powder on the surface, but before you take the print sample. This will remind you exactly how the prints were positioned enabling you to recreate the crime scene.
- Determine the surface you want to lift your print from. Use the appropriate dusting powder color. In some cases, a fluorescent dusting powder and UV light are used to make the prints stand out better. Take a little bit of the powder and gently apply the powder on to the surface. Once the dust settles, you should see some prints. The dust will bind to the oils left on the surface enabling you to make out the print.
- Carefully cut out a strip of tape and place it over the visible sample. When you lift the tape, you will notice the dusting powder has adhered to the tape in the form of the print.
- Press the tape with the print down on the clean index card. You will now need to label the print by identifying the time, date and location where it was obtained.
- Iodine fuming is another option to get a print. In some instances, it may be difficult to get a print using powders such as if the surface is soft or porous. The object that has the print is taken to the lab and placed in a special clear cabinet where the object is exposed to iodine vapors. This iodine then makes the print visible.
- Use a ninhydrine spray. This special chemical is sprayed onto the surface and reveals the print through a chemical reaction. The print becomes visible because it changes into bluish color so a sample can be taken.
- Now that you have a print sample, crime scene investigators will now cross check the print with a national federal database available only to law enforcement officials to find a match.
CSI people have the tools to properly lift a sample and have been trained not to contaminate a crime scene. If you are ever in one, call the authorities immediately and leave it up to the experts to take the prints and other evidence.