The definition of criminalistics "is the analysis, comparison, identification, and interpretation of physical evidence". The physical and natural sciences are used objectively in this branch. It is used to prove the existence of a crime or to make connections. "The criminalist provides information to investigators, attorneys, judges, or juries". - The Forensic Sciences Foundation, Inc. Career Brochure Web page
Evidence such as fingernail clippings and scrapings in an assault case, swabs for examination for sperm and seminal fluid, hair samples, and fibers on the deceased's clothing and body are sent to the Criminalist by the Forensic pathologist.
"Because there can be a variety of human activity that may surround the crime scene, the range of material which may be physical is almost limitless. Evidence may be so small that a microscope is needed to see it, or it may be a large as a truck. It may be as subtle as a whiff of a flammable gas at an arson scene or as obvious as a pool of blood at a homicide scene. The enormous range of material challenges the ingenuity of the criminalist. He examines and identifies hair, fibers, blood, and seminal stains, alcohol, drugs, paint, glass, botanicals, soil, flammable gases, and safe insulating material; restores smeared or smudged markings; and identifies firearms and compares bullets, tool markings, and foot prints". - The Forensic Sciences Foundation, Inc. Career Brochure Web page.
The criminalist uses analytical skill and practical experience to separate significant evidence from the rest. He sorts, compares, or identifies the evidence, developing useful information for an investigation or a trial. "The type of analysis that the criminalist does is difficult; it requires an eye for detail, a broad practical scientific background, and the ability to apply these skills in court with full knowledge of the ethical responsibilities involved". - The Forensic Sciences Foundation, Inc. Career Brochure Web page.
"Perhaps the most important task of the criminalist lies in interpreting the results of findings to determine the circumstances atthe time a crime occurred, or perhaps to support a witness' statement". - The Forensic Sciences Foundation, Inc. Career Brochure Web page.
"Reconstructing the events of a crime is often very difficult. It requires an understanding of human behavior, of the physical laws and processes involved, and the recognition of how they interact". - The Forensic Sciences Foundation, Inc. Career Brochure Web page.
"Finally, any findings must be conveyed to the other elementsof the criminal justice system. This is usually done by written reports or expert testimony. The criminalist must express conclusions so that technical details are understood by the court and the jury. The criminalist undertakes a serious challenge on behalf of society. - The Forensic Sciences Foundation, Inc. Career Brochure Web page.
Here is an example of criminalsitics taken from The Forensic Science Foundation's Career Brochure:
The Missing Murder Weapon
A 45-year old woman was found shot to death. Although the actual murder weapon was never found, excellent teamwork between the investigating officers and the criminalists enabled them to link the murder bullet to a specific weapon and, thereby, to a specific suspect. A detailed search of the murder scene revealed that all doors were locked. There were no signs of forcible entry and no indications of a struggle, burglary, or rape. The major portion of a .30-caliber, jacketed bullet was recovered from the wall behind the bed. Marks on the bulled indicated it might have been fired from a Remington rifle, Models 721 to 760. Neighbors reported hearing a loud bang or backfire the previous evening and seeing a red-and-white station wagon drive away a few minutes later, but were unable to give the license plate number or a description of the male driver. They said a similar vehicle had been parked near the victim's house on several previous occasions.
Two days after the murder, the police had gathered a variety of information, but it failed to fit a logical pattern:
- The victim had frequented a local dance studio, taking most of her lessons from one young, part-time dance instructor.
- The dance instructor owned a red-and-white station wagon. Inside his apartment, police found furniture that had been taken from the victim's house in a burglary some months before; a paper target with bullet holes, which appeared to be about a .30-caliber; and an electric razor and cuff links, belonging to a boarder in the victim's house, that were stolen in a separate, earlier burglary.
- The instructor claimed the furniture had been given to him by a friend. He denied knowledge of the murder, and denied having a .30-caliber rifle. He admitted visiting the victim the previous week and receiving a check from her for $140 as payment for a painting. Regarding the target, he said he had been to a local firing range where he fired a large caliber rifle; he refused to name the make and model.
- The instructor's next door neighbor told investigators his apartment had been burglarized three weeks earlier, and a Remington Model760 .30-'06 rifle was stolen, which he had reported to the police.
- The instructor was charged with first degree murder and was placed under arrest. Among his personal belongings at the time he was booked was a key to the victim's house.
The police were presented with a number of indications of guilt, but had no physical evidence to link the suspect to the crime. Since the murder weapon had not been found, the bullet recovered from the victim's bedroom wall became the basis for the scientific investigation. The suspect's neighbor, whose .30-'06 rifle had been stolen, provided three spent cartridge cases. Also, he guided investigators to a mountain site where, the previous Fall, he had placed rifle targets on a pine tree. A five-foot section of the tree was taken to the laboratory, where it was compared with the fatal bullet, revealing that both had been fired by the neighbor's stolen rifle.
At the firing range, the sign-in register showed the suspect had been there three days before the murder. The range master identified a photograph of the suspect as that of a man who had used the range within the previous month, firing a .30-'06 Remington model 760 rifle in Lane 28. Persons using adjacent lanes on that day confirmed the identification of both the man and the rifle. Several buckets of bullet fragments were recovered from Lanes 28,29 and 30 and taken to the laboratory. Rapid sorting based on size eliminated all but a few.
Comparative microscopic examination established an identity between two of the bullets from the firing range, the bullet from the pine tree, and the fatal bullet. Physical evidence was now provided.
The suspect's endorsement of the $140 check was used as a sample of his handwriting for comparison with signature on the firing range register. While making the comparison, the examiner found that the entire face of the check was traced, that the payer signature was traced from the victim's signature, and that the remainder of the check was traced from the suspect's handwriting, including his own name as payee. This check, number 330, was not in the sequence covered by the stubs in the victim's checkbook. The victim had received a new packet of checks recently. Four of these were found in an opened bank envelope on her desk, but the fifth book, containing checks numbered 325 to 349, was missing.
The dance instructor was charged with first-degree murder. After presenting the evidence, the prosecutor argued that:
- The victim was a lonely woman who had spent several thousand dollars for dancing lessons for recreation over a period of years.
- As the victim's dance instructor, the defendant gained knowledge of her habits, address, and financial situation.
- Through access to the victim's purse while she was at dancing lessons, the defendant stole a key to her house.
- Using the stolen key, the defendant made visits to the victim's house while she was attending dancing lessons with other instructors. During his visits, he had taken property-furniture, the boarder's razor and cuff links, and the checkbook-from her house.
- The defendant had stolen a .30-'06 rifle from his neighbor's apartment; he brought the rifle when he entered the victim's house.
- The defendant, practicing with checks 325 to 329 to perfect his forgery, finally was successful in forging check 330.
- After cashing the check, the defendant waited for the day he thought the canceled checks would arrive by mail at the victim's house. At this time, armed with the rifle, he entered her house intending to destroy the canceled check 330 in order to conceal the forgery. He encountered the victim unexpectedly and killed her.
The defendant was convicted and sentenced to life imprisonment.