Bloodstain-pattern analysis has been accepted as reliable evidence by appellate courts in one state after another with little or no examination of its scientific accuracy. Once one court ruled such testimony admissible, other states’ courts followed suit, often citing their predecessors’ decisions.

= sin A cos B + cos A sin B, we can find the sine of (45° + 30°) to give sine of 75 degrees. We now find the sine of 36°, by first finding the cos of 36°. sin 18°: Now, the sine of 18 degrees comes from the sine of half of 36 degrees.

Use trigonometric functions to determine if the impact angle for any given blood droplet. By accurately measuring the length and width of a bloodstain, you can calculate the impact angle using the following sine formula: c=opposite/hypotenuse=width(a-b)/length(b-c).

25.1 ft/sec

Class evidence places the suspect into a group of suspects. -Blood spatter- Droplets and patterns can reveal key evidence such as the type of weapon that was used in the crime, the time of the crime, and other details.

Blood, as it dries, darkens in color until, when completely dried, it turns reddish-brown or dark brown. An old, dried blood clot may become so dark that it is almost black.

Over time, spilled blood that starts out red turns darker and darker as it dries, and its hemoglobin breaks down into a compound called methemoglobin. As time passes, dried blood continues to change, growing even darker thanks to another compound called hemichrome.

Freshly dried bloodstains are a glossy reddish-brown in color. Under the influence of sunlight, the weather or removal attempts, the color eventually disappears and the stain turns gray. The surface on which it is found may also influence the stain’s color.

Fresh blood samples are not always viable due to difficulties in collection, transportation, or storage. However, viable and stable DNA samples can also be extracted from dried blood. DNA is usually extracted from one of two primary sources: cheek cells or white blood cells.

A study published in the International Journal of Legal Medicine reported that a blood drop on a hard surface in a typical indoor setting at 20 degrees Celsius is completely dry in 60 minutes.

Hepatitis B virus can live in dried blood for up to a week. Hepatitis C virus can survive for up to four days. Work surfaces that become contaminated with blood or other body fluids* can expose you to a bloodborne disease through cross-contamination.

Dried blood may carry the active virus, but it would have to enter another person’s bloodstream for infection to occur. Urine, sweat, and semen do not carry enough of the virus to pass it on.

Simply touching blood – even dried blood can be extremely dangerous. What appears to be “dry” blood may, in fact, have only been spilled hours before and therefore still have pathogens in it that are infectious. In the right environment, it could even still pass along diseases including HIV and more.

Once bleeding occurs, blood being ex vivo, it will coagulate and dry. During drying water evaporates from the blood pool until only the solid matter, mainly red blood cells (RBC’s), remains. Depending on the size of the pool and environmental conditions, the time the pool completely evaporates may take hours to days.

Blood has a lot of solids in it, and seems to dry faster because it only has to lose a little bit more water to become mostly a solid and therefore seem like a solid.