It seems to me the terms "back spatter" and "blowback" are rightly or wrongly interchanged? See following near bottom of link. That's why I normally state "back spatter/blowback".
http://www.crimescene-forensics.com/Crime_Scene_Forensics/Bloodstains.html
The source you just posted states the following:
"When a bullet strikes a target, some high force impact spatter may be directed back toward the gun that fired the shot. This is known as "back spatter""
It doesn't claim that back spatter and drawback are synonomous terms.
The Indian publicaiton you posted got DRAWBACK wrong. Drawback by definition is blood drawn into a weapon. It is not a synsonym for back spatter. Back spatter is blood projected out of a wound back towards the location of the weapon causing the wound. Going on about blowback has no bearing on the criticism I leveled which was he got DRAWBACK wrong. Blowback has several different meanings including unburned powder so is a useless imprecise term unless it is defined at the time of use. When blowback is used to mean drawback as your Indian source was using it, it is not the same thing as back spatter. Back spatter travels outside the weapon while drawback refers to what is sucked inside the weapon. To say that by sucking blood inside the weapon it gets on the shooter is outright stupid and extremely sloppy writing.
NGB stated the following:
"The whole issue of backspatter is problematical. First, there are two separate ways in which blood may end up on the shooter or his weapon, and these are often conflated. True backspatter can occur can occur when a bullet hits a body and can result in spots of blood being deposited on the shooter or the weapon. However this is unlikely to result in blood, certainly in any quantity, finding its way inside the gun barrel or sound moderator. There is also a phenomenon known as drawback or blowback, which results from pressure changes immediately following the discharge of the bullet. Gas can be drawn back into the gun barrel or sound moderator, and in the case either of a contact shot or a very close shot blood may be drawn back with the gas. This has been demonstrated with full bore weapons but it is by no means certain that this can be replicated with a .22 rimfire rifle.
The quality of expert evidence available to the defence at trial was very poor. Major Mead assisted the defence but in reality he was not a ballistics expert. Tests should have been conducted to examine whether drawback/blowback could occur with the Anschutz rifle fitted with a sound moderator. My personal view is that it could not, although I admit I have not carried out tests myself".
(I note NGB refers to "his" weapon. This is not the first time he has let slip sexism)
NGB is correct that without a contact shot that blood will not find its way in the gun very deep. He is wrong that 22 calibers haven't been demonstrated to result in drawback. On the contrary the seminal work in the field establish they do. That is why neither the trial defense nor the appeal lawyers have been able to find any scientific way to refute the prosecution assertion that Sheila's fatal wound would result in drawback.
Scipio your source in your OP is nearly 4 decades old. Forensics, physics/quantum physics has moved on since then. In any event it is clear you have misunderstood. Your source is saying he has experienced a few cases where contact wounds to the head with a small calibre weapon did not produce blow back/back spatter (blood entering the weapon) meaning that it was unusual.
My source is from 2012. It cites testing from 1977 that has proved to still be valid to this day and that is why so many different people TODAY still cite those test results. Those studies didn't include testing to the head other subsequent testing was done in the head area. My source didn't mention those studies but did mention actual experience where head shots from 22 calibers did not result in drawback. My source draws a DISTINCTION between head shots from 22 calibers and shots by 22 calibers to fleshy locations. The former do not produce spatter on a regular basis like the latter.
Not only did I understand this I used it to refute your nonsense about how Nicholas' blood would have to be inside the moderator if it was used. This source refutes your claim that nicolas; blood would be likely to get inside but supports the prosecution assertions about the neck shot.
You are the one who fails to understand not me, I understand the issue extremely clearly.
I stand by my claims:
- The closer the wound is to contact the more likely it is to produce blow back/back spatter
BUZZ WRONG. Back spatter is not a function of the distance of the weapon from the wound. Back spatter depends upon the location of the wound specifically whther the channel made by the wound will fill with blood and air and then the closing of the wound by elastic tissue will force the material in the channel outside of the body. The distance of the weapon from the body makes no difference in whether backspatter will occur. The distance of the weapon detemrines whether the spatter that comes out of the wound will reach the weapon/shooter. If the weapon is within range of the spatter it will get on the weapon/shooter. If it is very close then it can get inside the weapon. The source above provides the distances required for blood to get inside up to 5mm deep. To go beyond that it needs to be a contact wound.
- The larger the calibre of weapon the more likely it is to produce blow back/back spatter
BUZZ WRONG. In general the larger the caliber the further the back spatter will travel and the more backspatter there will be because the wound channel is larger and thus mor emateiral fits in that channel to be projected out. However some high caliber bullets with low velocities can produce less spatter or spatter that travel less distances than smaller rounds with a higher velocity. So generlaizing only can go so far.
In wound locations where there is a small amount of tissue over bone that is close to the body surface back spatter is less likely to occur and mostly will occur from larger caliber rounds.
- The anatomical location is another important factor. A head wound is far more likely to produce blow back/back spatter than a wound elsewhere
BUZZ WRONG. You are right that anatomical location is important but totally wrong in your claim that head wounds are more likely to result in back spatter. Head shots are the least likely locations to result in back spatter because there is bone covered by a small amount of flesh. The head lacks the elasticity and blood flow of other regions.
> this is a bullet channel in tissue, the point is where the bullet is while the rest is the wound channel made by the bullet. When the channel closes the material in it including the air in it is propelled int he opposition direction of the bullet so is projected out of the wound. That is back spatter 101. The more elasticity of the tissue the more air flow and thus more projection force. The head has less tissue elasticity than other regions of the body.
- Bullet size is also an important factor. The larger the bullet size the more likely it is to produced blow back/back spatter.
Only half right. The larger the bullet the larger the wound channel and thus larger the volume of back spatter and
in general it will travel further. In locations not ideal for back spatter to occur (where there is not much elastic tissue0 the larger the caliber the better the chance of some spatter occurring nontheless. This doesn't somehow equate to it being unlikely for 22 claiber rounds to be able to cause back spatter in locations ideal for it to occur.
- Angle is another factor.
I am not going to pretend I am some sort of expert in all of this because I am most definitely not but our links above support my claims and surely a basic understanding of physics will tell you that the conditions most likely to produce back spatter/blow back did not exist with SC's wounds:
Factors most likely to produce blow back/back spatter -V- SC's wounds
- Contact shot - V- Unclear whether contact or close contact
- Large calibre weapon - V -Small calibre weapon
- Large bullet - V -Small bullet
- Head wound - V - neck wounds
It is also questionable whether blood from blow back/back spatter would travel as far into the silencer as it was 'found' and whether it would have distributed as a flake &%+((£
Not only are you not an expert you have everything backwards and wrong. You took an unsupported erroneous claim from an Indian source and from that you jump to various wild conclusions.
It didnt't judge the likelihood of a 22 shot to the neck resulting in spatter. All it did was assert a head shot form a high caliber weapon is even more likely to result in spatter than a body shot from a 22. That doesn't equate to saying a body shot from a 22 is unlikely. In the meantime location in the head is a significant factor of whether a shot will result in spatter just suggesting any headshot from a high caliber is going to cause spatter in not really correct. What he wrote was very short and never explained in full.
Trying to pretend it establishes a contact wound from a 22 calibers in the location Sheila suffered her fatal wound is unlikely to result in spatter is a joke. you need to find someone who specifically addresses that lcoation and has solid evidence to refute the prosecution assertions. It is not a coincidence that the defense has failed to come up with anyone who could do that.
