A hammer and a knife are two entirely different weapons. But you got me thinking so I did a little experiment (hence the delay in responding). I already had a claw hammer on my deck so I grabbed a knife, a bucket of water and went outside to see if swinging these two weapons, if you will, resulted in the same patterns.
First I took a few practice swings with both dry and noted the difference of how I handled each weapon pretending I were trying to hurt someone. Holding the hammer the first thing I noticed was that my weapon's point of impact was roughly 18 inches above my thumb. As I swung the hammer I noted that the area of the hammer that would collect blood (and thus cast it off) went so freely behind my back that I accidently hit my back with the claw. I did this experiment only while standing up. I would have done more experiments with the hammer but that wasn't the weapon used in this case. I only used it to see if there would be a difference between the two weapons and their resulting cast off.
Next I did the same thing with a kitchen knife that has an 8 inch blade using just my right hand. The first thing I noticed with the knife was that my point of impact (and where the blood would be cast off from) was roughly 9 inches below my pinky. Standing up swinging I noticed that no matter how hard I tried I could never get the tip of the blade to go freely any further back than my elbow which always remained in front of me. The only time I got the point of the knife to go behind my shoulder was by tilting my wrist back once I was at the furthest that my arm could naturally go and even then it was hard to do and very awkward. Nothing I could imagine doing naturally in a fit of rage. The second thing I noticed was that with every upward swing the pinky side of my hand would curve out to the right. Then I stabbed with both hands. I could not get the tip of the blade behind my head unless I again tilted my wrists back.
I then did the same thing on my knees with one hand and then with both hands with the same results as standing up. Last, I did this on my hands and knees. I could only use one hand as the other was busy holding me up. With this experiment the results differed quite a bit. No matter how hard I tried the blade tip always faced down. I again went to the furthest my hand would naturally go back and tilted my wrist to see where the blade went. It still faced downward and away from my body.
Then I got my bucket of water. I experimented with the knife first simply because that was the weapon used. First I stood with my back facing about six feet from a wall. I took ten normal stabs and two with a two second breather with the knife as far back as possible. There was water behind me but it was off to my right about four feet away from me. There was no water on my back. I then took ten swings holding the knife with both hands facing the wall and ten swings away from the wall (again dipping into the water with each downward stroke as if it were my victim to reload my cast off). I also took a few 'breathers' at my furthest point back. I still had no water on my back. I estimated that I took no less than thirthy five stabs and had no cast off on my back to show for it.
I then did the same experiment with the hammer dipped in water holding and swinging as naturally as I could. I only did this with one hand as it was not the weapon used in the crime and was only used to see if cast off from the hammer differed from the knife. I dipped (only the nail end to collect water) and swung. This time I got cast off on my back on my first swing. I took ten more swings with one hand but that was enough to prove to me that a knife and hammer have different cast off patterns.
So.... after I did my unscientific experiment I thought maybe I should provide a link specifically siting cast off patterns of a knife. I found this:
http://www.enotes.com/forensic-science/cast-off-blood
Which says "The blood is usually flung away from the arc of movement, which means that it tends to land on nearby surfaces,
rather than on the attacker." But while doing that search I found something that rather shocked me....
http://books.google.com/books?id=Cm...onepage&q=cast off trails blood knife&f=false
And please do open the link as I showed you the same respect by looking at your research. First and foremost note the author of the book. That is the same Tom Bevel who testified against Darlie. Hopefully the link opens to the page at issue but if not it's page 236. The very first thing you should see is a student holding a hammer. This picture is labled figure 10.9. Down further on the page is a "case example" which clearly describes the Routier case. The picture (Figure 10.10) on the next page shows the results of the experiment from figure 10.9 with cast off of the experiment on numerous places on both sides of the student's back. The picture beside it (figure 10.11) shows the back of Darlie's shirt as a comparison to figure 10.10 as proof that cast off blood from her swinging the knife ended up on her back. And please don't just count that one drop. Read Bevel's own words where he clearly states only one drop of one victim's blood was on her back. There wasn't sprays of blood. There wasn't even multiple drops from both victims. There was a single, solitary drop of blood..... blood from the son she says woke her up.
There's only two problems. One, the weapon in the Routier case was definately a knife, not a hammer. There was no need to do the experiment with the hammer unless a knife couldn't produce results that even remotely duplicated the cast off on Darlie's shirt. Had I been Bevel I would have felt compelled to prove that a knife (not a person) could produce that cast off pattern found on the back of the assailants shirt. Two, a knife and a hammer have two different cast off patterns (at least from my experiments and Bevel's as well as it seems since he opted for a hammer as opposed to the actual murder weapon). Bevel's own experiment showed that a hammer produced nothing remotely similar to the cast off on the back of Darlie's shirt yet he claims his experiment with the hammer replicates the spatter on Darlie's back. I'm certainly no scientist but I counted eleven spatters on the student's back and one on Darlie's back (as per Bevel's figure 10.11 which reads "this single spatter..."). I'm sorry but how exactly does eleven cast off spatters in all directions from a hammer compare to one one drop from a knife? And why isn't he doing experiments with a knife to prove spatter would produce the same (or similar) drop on her back?
I did the experiments myself and I know exactly why he opted to use a hammer over using the actual murder weapon in his experiments. The knife (which is definately the murder weapon) wouldn't produce the spatter found on her shirt. I've looked at this a number of ways. What I come down to is this.... the prosecution layed out a scenario of the above that isn't forensically possible along with a time line that noone could manage to do. I consider myself fit and I was exhausted just thinking about all that needed to be done in the two minutes she had to do it in.
Darlie claims she doesn't remember the attack (which to me seems plausible based on my experience). It's possible and very likely Darlie was attacked first (she was either the target all along or as the adult in the room she was the one that needed to be immobilized first due to her comparable strength). She made noise in the struggle, woke one or both boys but at some point passed out. Now that one or both of the boys are up the attacker either fears being identified by them or fears they will alert other adults with their screams. The attacker then goes after the boys while Darlie is unconscious or he presumes dead since he stabbed her shoulder (which in the dark he could have thought was closer to heart), slashed her thoat, and did whatever else to her as evidence in the photos.
At some point Damon crawls to the couch where Darlie is and tries to wake her. Who knows at what point this is but it's plausible that Darlie is laying on the couch passed out facing away from the attack. Damon tries to get to her but is attacked from behind. As he is standing in front of his mom who is laying with her back to him he is stabbed in the back. The stabs cast off Damon's blood onto Darlie's back. Based on her memory she wakes up because Damon hits her shoulder. By then the attacker assumes they are all dead and is turned around heading out (either because his plan to to do a simple robbery went wrong, his plan for a simple rape went wrong due to the kids in the room or his plan for a simple hit went went wrong). Either way Darlie appears dead (and based on what he thinks he did to her he thinks she is) and he is certain all the witnesses are dead (or at least near enough to death that they will not be physically able to immediately alert another adult for help before he can safely get away).
I know it's long but so are trial transcripts.
