Skip main navigation

Item examination, presumptive testing and DNA sampling

Forensic items are examined for biological fluids to identify material to send for DNA profiling. Watch Gabriella Mason-Buck explain more.
OK, Natsumi, now we’re going to take a look at the metal bar recovered from Nelson’s Dock. OK. If you have a look at the end here, you can see some brown material. What I want you to do is with the swab that’s on the bench is, I want you to swab that area. OK.
Like this? Perfect. Now what I’m going to do is take a piece of filter paper. I’m going to fold it into a triangle.
I’m then going to gently scrape the end of the material that you’ve just collected. OK.
I’ll place that down onto the bench, and then I’ll take the swab from you. And this is what we will send off for DNA profiling later, if there is a positive reaction for blood. OK. Now we’re going to carry out the hydrogen peroxide and Kastle-Meyer test as we did before. So taking a couple of drops of hydrogen peroxide, directly placing it onto the material that we’ve just collected.
And then I’m going to time the reaction of the Kastle-Meyer onto that location. Yes.
As you can see, the colour change has occurred very quickly. Yep. I believe that there is blood on the end of this item. So this swab that you have taken along with the swab that was recovered from Nelson’s Dock will be now taken to Federica for DNA profiling. OK.

Examine the metal bar recovered from the crime scene for biological fluids to identify material that can be send for DNA profiling.

This article is from the free online

The Science Behind Forensic Science

Created by
FutureLearn - Learning For Life

Our purpose is to transform access to education.

We offer a diverse selection of courses from leading universities and cultural institutions from around the world. These are delivered one step at a time, and are accessible on mobile, tablet and desktop, so you can fit learning around your life.

We believe learning should be an enjoyable, social experience, so our courses offer the opportunity to discuss what you’re learning with others as you go, helping you make fresh discoveries and form new ideas.
You can unlock new opportunities with unlimited access to hundreds of online short courses for a year by subscribing to our Unlimited package. Build your knowledge with top universities and organisations.

Learn more about how FutureLearn is transforming access to education