Forensic evidence isn’t just fodder for TV crime dramas. Forensic studies are pivotal investigations that aim to link suspects to criminal activity. Forensic evidence is any criminal evidence that is acquired through scientific means during these investigations. Forensic evidence includes biological evidence based on individual identity markers, such as finger and palm prints. Investigators also look for any possible DNA specimens that might identify a potential suspect. Since DNA is found in all parts of your body, specimens can include hair, skin, nails, and bodily fluids. DNA helps investigators find criminals because DNA sequences are unique to each individual, though close family members will have a slightly similar DNA structure, too.
Forensic science technicians either work in the field wherever there are active crime scenes or in a laboratory. According to the U.S. Bureau of Labor Statistics, many forensic science technicians who work for police departments are actually sworn officers themselves. When they are in the field, forensic science technicians assess the scene of the crime to decide what is evidence. Anything from biological remains to weapons used at the crime scene as well as footprints, tire tracks, and fibers from upholstery and clothing can be used as evidence.
Once evidence is identified, the crime scene investigators must determine what tools are needed to collect it. Common tools include cotton-tipped applicators, sterile water, cardboard swab boxes, paper bags or boxes, plastic tubes for sharps, and plastic-windowed forensic envelopes. Specialized heat-sealed bags are recommended for technicians dealing with fire debris at an arson crime site. Devices like tweezers or forceps are traditionally used to avoid contaminating any evidence before its transfer to the lab. All evidence must be carefully logged to establish a credible chain of custody.
Forensic science technicians also chronicle the crime scene as evidence itself, taking care to capture everything exactly as it appears. They may make hand-drawn sketches, take photos and videos, and make notes about how objects are positioned or where they might have landed or been placed. Digital evidence may also be collected. Technicians use this information not only to re-create the crime scene but also to write their formal report.
Bloodstain pattern analysis, or BPA, is also a key part of forensic evidence. Bloodstain pattern analysts are special investigative agents who compile information based on the location, amount, shape, and distribution of any blood at the scene. By evaluating the blood spatter pattern, they construct a hypothesis of the events leading up to the bloodshed. The bloodstain pattern analyst’s findings can determine important details like the type of weapon used, the type of trauma inflicted, and where the victim was standing or sitting.
Once the evidence is in the lab, forensic science technicians conduct studies on evidence visually, chemically, and biologically. They may also consult with other experts like toxicologists, dental experts, medical examiners, or firearm and explosives specialists.
When forensic evidence goes wrong
There are ways a lawyer can challenge the accuracy of forensic evidence. By law, a defense attorney can disprove or cast doubt on any real evidence, demonstrative evidence, documentary evidence, or testimonial evidence that has been presented.
Let’s take a look at a few scenarios in which real, demonstrative, documentary, and testimonial evidence can possibly be disproved.
The scene was inaccurately diagrammed or measured. Diagrams made by forensic science technicians and submitted to a case are a form of demonstrative evidence. Maybe the BPA had details that didn’t seem consistent with the crime scene. A Franklin defense attorney can hire an independent BPA analyst or other specialists to review and reexamine questionable evidence to disprove – or cast doubt on – the accuracy of the primary investigator’s report.
Maybe the investigator made an error measuring or re-creating the crime scene. Investigators may rely on fairly cheap tools like basic mapping software and low-tech surveying equipment. The appeal of this equipment is that it is generally accessible and easy to use. State-of-the-art scanning tools (like 3-D lasers) are more expensive, and require more training, but they produce higher-quality imaging. A defense lawyer can argue that an inexperienced crime scene investigator using subpar tools made a poor calculation.
Evidence wasn’t properly logged or tagged. Real and demonstrable evidence includes objects you can touch and hold in your hand. Once a piece of demonstrative evidence is in custody it must be logged and categorized properly and consistently by forensics. If an item wasn’t labeled properly when it was collected from the crime scene, it’s no longer a certainty that the item being presented is the original piece of evidence itself. If an item isn’t handled with an acceptable level of integrity, a defense lawyer can question the chain of custody.
Evidence wasn’t properly stored or treated. Maybe an item wasn’t carefully packaged or transported when it was collected from the crime scene. A liquid was put in a porous container rather than a nonporous vessel, and it leaked in transit. The improper packaging caused the cross-contamination of multiple pieces of evidence. An experienced Franklin defense lawyer can question whether what was submitted meets the qualifications of admissible evidence.
The crime scene wasn’t fully searched. Maybe some evidence was missed because the technician neglected to use a proper forensic light source such as a UV lamp or laser. These lights operate with enhanced wavelengths that can expose fingerprints, body fluids, fibers, footprints, ballistic and explosive residues, and also traces of drugs. Certain types of specialized lamps can even expose forged documents. The defense lawyer can bring in an expert witness to testify that the wrong tools were used and key evidence was overlooked.
The evidence may not be admissible in court. A dental expert – or forensic odontologist – sends an email to an officer about one of the officer’s cases. The odontologist weighs in on the case in the email but does not appear in court as a witness. The email is printed out and presented as documentary evidence in lieu of witness testimony. The defense lawyer can argue that the document is hearsay and not admissible in court.
When it’s time to call a Franklin defense lawyer, call us
If you’ve been charged with a criminal offense, you need to get a lawyer as soon as possible.
An experienced defense lawyer will work to establish that the prosecution cannot prove its case beyond a reasonable doubt. If they cannot prove that you, the defendant, are guilty, you cannot be convicted of the crime as charged.