Lesiones y lesiones leves: panorama provincial

PRINCIPLE

Much of criminalistics is based on a scientific law called Locard’s Exchange

Principle, which states

that “whenever two objects come into con- tact, a transfer of materi- als occurs.” This transfer may be minute, but with proper equipment and training a criminalist can find the transferred materials, analyze them, and derive information from them.

explosive device) contained in a blasting cap and triggered by an electric charge.

The investigator should examine the scene of an explosion as soon as possible, before the evidence is obliterated. Bombing investigations generally focus on four separate areas. The first is to examine the components of and residues left by the bomb and try to link them to the person(s) who built the bomb. Explosives almost always leave traceable residues in the crater and surrounding areas. Microscopic examination of materials from the scene lets characters find these unexploded particles, which they can then iden- tify with a chemical color test. Explosions also leave distinctive marks, called pitting and crater- ing, in metals; and the direction and type of soot on the walls is likewise important. Remnants of the materials used to construct the bomb (such as the metal fragments created by a pipe bomb) are another type of explosion evidence. Also, the faster (stronger) an explosive is, the more damage it does, so the extent of the damage can tell inves- tigators what type of explosive was used.

Second, investigators can compare the bomb- er’s “signature” to known signatures. Each bomber tends to have his own particular method or style of making bombs. Even if they know other ways to make bombs, they usually keep using certain techniques that they favor. SS: Psychology/Crimi- nal Psychology can act as a Complementary Skill to Criminology for purposes of determining a bomber’s “signature” and what it might mean. (Of course, a highly-skilled bomber in an adventure story might vary the types of bombs he uses, just to confuse the characters.)

Third, investigators look for evidence of items associated with a bomb, such as the vehicle or pack- age it was carried in, and try to link those with the bomber. They also interview witnesses, since the color and shape of an explosion can provide clues.

Fourth, investigators look into the motive for the bombing. They try to find out who had a reason to set off a bomb in this particular place, be it a disgruntled neighbor, a business enemy, a fanatical terrorist, or someone else.

BLOOD

Blood samples and stains can be extremely important clues. They can help identify murderers and show what happened at a murder scene. The study of blood (and other body fluids) is known as Serology. SS: Serology serves as a Complementary Skill to Criminalistics.

The basic steps in a blood investigation are these:

■ is it blood?

■ if so, is it human blood?

■ if so, what are its characteristics (i.e., whose blood

is it)?

Special chemical tests provide the answers to these questions.

Characters should gather blood samples while the blood remains as fresh and pure as possible. As blood dries and ages, it gradually becomes more and more difficult to determine its characteristics, because the red blood cells rupture. Impurities can also occur when blood mixes with other sub- stances, such as dirty water. However, in some situ- ations the age or purity of blood is less important (for example, the precipitin test, described below).

Characters can detect “occult” blood stains — those which are hidden, too small to be seen by the naked eye, or have been cleaned up — with chemi- cals such as luminol and fluorescein. Luminol reacts to blood by creating a blue-white to yellowish-green light for about 30 seconds after exposure; this light is visible to the naked eye and should be photographed before it fades. Fluorescein works similarly, but is only visible under ultraviolet light. Even well-cleaned crime scenes usually retains microscopic traces of blood which become very visible when treated with these substances — luminol, for example, can detect blood in dilutions as small as 1 in ten million.

Identifying Blood

Determining that a sample is in fact blood is usually a simple matter — the examiner uses a chemical test, such as a catalytic color test. In game terms, this requires a Criminology roll, usually with a +1 to +3 bonus. The GM may reduce the bonus to +0 if the sample is contaminated, aged/putrefying, or otherwise difficult to work with.

After identifying a sample as blood, the exam- iner has to confirm that it’s human blood and not animal blood. Several different tests, including the precipitin test, can provide this information. Unlike the catalytic color test, the precipitin test gener- ally isn’t affected by the age or purity of the blood sample, so a Criminology roll at +1 to +3 is enough to perform it properly.

Blood Characteristics

Scientists identify blood by its “type.” The most common blood typing system is the A-B-O system, but more than 15 others, such as ADA, M-N, and Rh, are also used. Serologists can also identify cer- tain enzymes and proteins, known collectively as “genetic markers,” which exist in blood; these are much more reliable than simple blood types. Blood cannot as yet be “fingerprinted,” i.e., matched to a specific individual, except through DNA typing (see page 148). But by determining a blood sample’s type in each of the classification systems, and iden- tifying the genetic markers, a serologist can estab- lish what percentage of the population has that specific blood type. If a suspect has that type, that fact is of some evidentiary value — the lower the percentage, the greater the likelihood that the sus- pect is the perpetrator. (Theoretically, if all genetic markers were present and could be positively iden- tified, the odds of two people having the exact same “profile” of blood characteristics would be about one in 1.3 billion; however, many characteristics are obscured or destroyed as blood ages and dries out.) Another way to further individualize a blood sample is to analyze the blood enzymes in it; this method can identify the blood by racial type.

Sometimes a criminalist won’t have a blood sample, but will have a sample of some other body fluid (for example, saliva left on the rim of a glass or in a bite mark on the victim). If a person is a “secretor,” then an analyst can determine his blood type from his other bodily fluids, such as saliva and semen. Approxi- mately 80% of the populace are secretors. (The GM should assume all characters are secretors unless he has reason to rule otherwise.)

As mentioned above, the fresher and purer a blood sample, the easier it is to work with. Red blood cells rupture as blood dries and ages, making analysis more difficult; impurities in a blood sample can also cause problems. In some situations, char- acters can use a technique known as electrophore- sis on dried blood to separate it into its component parts (including DNA) for analysis. Additionally, a test called the absorption-elution technique can type blood samples up to eleven years old, but it’s more complicated and difficult than standard tests. Depending upon the age and purity of a blood sample and the equipment available to a character, the GM should assign a -1 to -5 penalty to a char- acter’s Criminology roll to analyze it.

Transfusions sometimes obscure blood test results. If a suspect from whom a blood sample is taken has had a blood transfusion within the 60-day period prior to the taking of the sample, obtaining a valid sample is not possible. A clever

Dark Champions criminal might use this fact to

his benefit.

Blood Splatters

Besides its capacity to help identify an offender, blood can also provide information based on the way it stains and splatters the crime scene. For example, a large pool of blood at the crime scene often indicates the victim was alive for some time after the wound was inflicted, since after death the heart stops pumping blood through the body (and out of the wound). On the other hand, some fatal wounds may cause little or no blood to leak out of the body.

The size and shape of a blood pattern can indicate which direction the blood came from, what angle it hit the surface at, where the attacker stood and what hand he wielded the weapon with, and other information that helps a criminal- ist reconstruct the events of a crime. Analysis of blood patterns is an extremely complex process; at his option, the GM should assess Criminology roll penalties of -3 to -6 unless a character has SS: Bloodstain Interpretation as a Skill (which also serves as a Complementary Skill).

Blood Tests

In some cases, characters can test a person’s blood to determine if he’s taken drugs or was poisoned. Tests can detect amounts of foreign sub- stances as small as one nanogram (one billionth of a gram) per milliliter of blood, depending on the substance and the test used.

COMPUTER FORENSICS

Computer forensics involves obtaining lost, encrypted, or deleted data from intact computer storage media (such as hard drives and CD-ROMs), or retrieving any sort of data from broken or dam- aged storage media. It’s a function of the Computer

Programming Skill, not Criminology; see page 126.

DNA “FINGERPRINTING”

DNA, deoxyribonucleic acid, exists in the nuclei of living cells. Even a tiny sample of tissue (for example, a drop of blood, the root of a hair, sweat, saliva left on the back of a stamp or other object that’s been licked, or even excrement) con- tains DNA. Each person’s DNA is unique (unless he has an identical twin) — and unlike blood charac- teristics, DNA does not deteriorate with age unless it’s exposed to radiation (such as sunlight). This provides forensic scientists with an important tool.

Modern science has not yet reached the point where it can quickly and easily identify each person’s DNA with absolute accuracy, but it can determine the frequency with which a particular sample of DNA occurs in the population with such accuracy (such as one in one hundred million per- sons) that it suffices for the purposes of forensics. The FBI has a database, CODIS (Combined DNA Index System), that lets scientists compare DNA samples from crime scenes to samples from known sex offenders and other violent criminals. Analy- sis of DNA can also sometimes reveal its general ancestry (e.g., European, Asian, or African-Ameri- can). Researchers hope to develop systems that can determine hair color, and perhaps even facial char- acteristics, from DNA.

There are several major methods of DNA typing. The first is restriction fragment length poly-

morphism (RFLP), which requires a fairly large and

fresh sample to analyze. In this process, a technician uses restriction enzymes to cut chromosomes into hundreds of DNA fragments, some of which con- tain “tandem repeats” (sections of DNA in which the bases that form DNA repeat many times). He then sorts the fragments through electrophoresis and transfers them onto membranes. Treating the membranes with radioactive “probes” allows him to identify the fragments. By using multiple probes, the technician can reduce the frequency of occur- rence of the sample to the point where it occurs in frequencies estimated to range from one in one hundred million people to one in 30 billion people. But while highly accurate, the process can take as much as three to twelve weeks.

Another major technique is polymerase chain

reaction (PCR). PCR works on very small samples

(as small as one-billionth of a gram of DNA, such as might be obtained from the saliva on a cigarette