My apologies if already covered, and maybe more approriate in decomp thread...
Still...if a water disposal was involved, can anyone summarize the basics on a body surfacing? IIRC, this occurred in the Peterson case.
I suspect, if the body is tied to a weight to keep it submerged doesn't this loosen and detach as the tissue decays away after bloating? Time for this to occur?
If a body is totally encased in something (e.g. suitcase) with weight contained within, does this provide more assurance it will stay submerged until the construction material decompose as well?
All of the rising and falling water levels over the last couple of months would have encouraged a water disposed body to surface, wouldn't it?
TIA!
Just to sink the body, some factors need to be considered, such as how the body is positioned. If it is 'up and down', then the density of the body assists additional weights in overcoming the buoyancy issue. It is the density of an object, not its weight that determines displacement of the surrounding liquid.
When you lay the body out flat, horizontally, the density factor is decreased as the same amount of weight is spread over more area. This causes a body to float easier because buoyancy is helping to raise it up.
Anyone who doubts this can easily can test the theory (please, without weights attached). Step into a swimming pool feet first in a depth over your head, and you will sink beneath the water (without using either your arms or legs to introduce propulsion into the equation). Then lay out flat in the same pool, and you will float.
This is not because you have air in your lungs and a deceased person doesn't, because even when you stepped into the pool feet first, you still had air in your lungs. This is not because you weigh more standing up than you do lying down, because you weigh the same in either situation.
Regarding buoyancy in general, Archimedes Principle says: "Any object, wholly or partly immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object." Repeat: Any object, wholly or partly immersed in a fluid, is buoyed up by a FORCE equal to the WEIGHT of the FLUID displaced by the OBJECT.
Upward FORCE = Weight of the Fluid
The fluid in this case is water. The weight of water is 62.4 lbs per cubic foot, or 8.5 lbs per gallon.
The object in this case is the body. A human body typically (size and shapes vary) will displace 1.5 cu. ft. of water in a vertical position and 4 to 5 cu. ft. of water in a horizontal position.
So back to our previous experiment: if you weigh 150 lbs -- you refenced the Peterson case and this was Laci Peterson's weight -- and step into the water, displacing 1.5 cu. ft. of water when you do, you will be buoyed upwards 93.6 lbs. Since you weigh 150 lbs, you then subtract 93.6 from 150 to obtain a negative buoyancy of 56.4 lbs., meaning you sink.
If you were lying down and displacing 4 cu. ft. of water, your buoyancy factor increases. 62.4 * 4 = 249.6 - 150 = 99.6 lbs of positive buoyancy, meaning you float.
Given those simple physics as calculated, it would take roughly 50 lbs of weight to cause a person to sink if they were tied to their feet, and roughly 100 lbs to sink the same body if the weights were divided and were tied to each of the 4 limbs and the body was horizontal.
Now advance time and decomposition into the equation. As internal gases expand within the decomposing body, the buoyancy factor will increase requiring more weight to hold the body down. A body is known to bloat to over 3 times its normal size, so now the displacement factor is not 4 cu. ft, but 12 cu. ft. [62.4 * 12] = 748.8. lbs
Obviously, Laci Peterson's body did not surface with 748.8 lbs of weight attached to her. But neither did it surface with the 30 lbs. of allegedly unaccounted for cement that Distaso suggested in his closing argument was what kept her down, which was a truly absurd proposition.
HTH
rg on how to kill flies.
