Skeleton Keys Is Named A Top Forensics Blog

We were thrilled to find out yesterday that Skeleton Keys was named by ITSGOV as one of the top forensics blogs on the Web. ITSGOV is a comprehensive crime scene investigation resource, and they have compiled a list of the top blogs that cover forensic science in its many forms. From the point of view of anyone who writes mystery or crime fiction, it’s a terrific resource on multiple levels.

We were thrilled to be included in such an impressive list of coroners, criminal profilers, lawyers, and bioarcheologists as well as forensic scientists, pathologists, psychiatrists, artists and anthropologists. Their list of top forensic science blogs can be found here, where they describe Skeleton Keys as ‘the blog of Jen J. Danna, a Canadian forensic crime fiction author, who shares some remarkable insights in her musings.’

On behalf of myself and Ann, the partner behind the writer here on the blog as well as in our fiction writing, thank you to ITSGOV for including us!

Forensics 101: Epiphyseal Fusion

Last week, in an overview of how to determine the age of a skeletal victim, I mentioned a process called epiphyseal fusion. We’re going to delve into that topic in more depth today.

In the picture above, forensic anthropologist Dr. Bill Bass holds two bones ― an infant and an adult human femur. How do tiny infant bones mature to an adult size that could be as much as five or six times bigger? The answer lies in long bone growth.

Long bones have three distinct sections ― the diaphysis, or shaft; the metaphysis, or the flared end of the shaft; and the epiphysis, or end cap of the bone. Long bone growth takes place at the epiphyseal or growth plate, located between the metaphysis and epiphysis. In the picture below, all three sections of bone are clearly visible in a knee x-ray of a young person. All three bones, the femur above, and the tibia and fibula below, show the gap where the growth plate still exists.

The growth plate itself is made up of a scaffold of cartilage. Osteoblasts, the fibroblast-like cells responsible for bone creation, are laid down on this scaffold. The osteoblasts produce a collagen matrix that is then mineralized to become new bone. If growth is still ongoing, more cartilage is laid down on that bone as the growth plate moves farther away from the center of the shaft, and the process repeats. When maturity is finally reached, growth stops and the epiphysis and metaphysis permanently fuse together. The x-ray below shows a normal adult knee. As you can see, no trace of the growth plate remains and epiphyseal fusion is complete.

The key to epiphyseal fusion in a forensic setting is the information it can give about a victim’s age at the time of death. Each bone has a predictable age range when long bone fusion occurs; in fact, different ends of the bone each have their own individual range. The table below gives examples of five different long bones and the expected age where epiphyseal fusion occurs. Until that point, the end of the bone is a distinct and separate piece from the shaft.

As you can see from these examples, age determination is not an exact science. Ranges of fusion can span five, or even ten, years. If a full set of remains is available, a forensic anthropologist will use multiple bone markers to make his best age estimation; if only partial remains are available, then the best estimate possible will be made based on whichever bones are present. If the victim is an adult and even the medial clavicle ― the very last fusion point ― is fused, then an alternate method of aging must be used. We’ll look at one of those different techniques in our next Forensics 101 post.

Ann and I are going to be taking a few weeks off from blogging to enjoy the chaos of the season and to hopefully take advantage of the time to concentrate on our writing. But we’ll be back on January 3, 2012 with our first new blog post of the year.

From both of us to all of you, happy holidays!

Forensics 101: Determining Age of a Skeletal Victim

In our last few Forensics 101 posts, I covered two aspects of victim identification: time since death and sexing a victim based on the skull or the pelvis. In this post, I want to open the discussion on age determination of skeletal remains. This is a complicated topic so we’ll start with an overview first and next week we’ll start to get into the specifics.

A forensic anthropologist can use multiple skeletal characteristics to determine the age of a victim at the time of death. Some characteristics can only be used to determine the age of pre-pubescent victims, some apply to adult victims.

Let’s look at these two groups:

• Pre-pubescent: The skeletons of children and teenagers are in a constant state of flux.
  1. Infant fontanelles close with the union of cranial bones.
  2. Long bones are constantly growing, allowing for increased limb length.
  3. The growth plate of long bones is constantly laying down new bone until maturity is reached; at this point, the end of the bone fuses to the shaft, terminating growth.
  4. Teeth are lost and new teeth form and erupt in their place.
• Adult: Due to the lack of growth in the post-pubescent years, age determination of adults is slightly more difficult, but there are several very valuable characteristics.
  1. The surface of the pubic symphysis (where the two halves of the pelvis meet at the front of the body) changes significantly over time, with those changes continuing into the senior years.
  2. Similar changes are seen at the auricular surface of the ilium (the hip bone).
  3. The medial rib ends (at the center of the body, where the ribs join with the sternum) also change with age, both the surface of the bone as well as the shape.
  4. The sutures in the skull and palate finally fuse, and, with time, become completely obliterated.

All the above changes tend to occur at relatively predictable ages. Based on these characteristics, or, ideally, based on multiple characteristics combined, a forensic anthropologist can accurately estimate the age of a victim at the time of death.

Next week, we’ll look epiphyseal fusion in children and teens, showing how the fusion of the bone end to the shaft as maturity is reached can reveal the age of a young victim.

Photo Credit: fruity monkey