Forensic Science In The 1970s

The Actual Work

Forensic science in the 1970s was not glamorous. It was mostly applied chemistry and basic biology, done in windowless rooms with budget constraints that still sting when I think about them. The equipment was real but limited, the techniques were crude compared to today, and the conclusions were far more honest — and far less dramatic — than what television eventually sold the public. Most crime labs at the time handled caseloads that would seem abusive now. The expectation was not to run everything on a piece of evidence. The expectation was to figure out what was worth running, and what would waste everyone's time.

What We Actually Called Forensic Science In The 1970s

The standard toolkit was small. Blood typing was the foundation. You took a stain, you treated it with anti-A, anti-B, and anti-A,B reagents, and you watched for agglutination. That told you the ABO group. If you had an antibody screen kit, you could also determine the MNS and Kell groups. That was it. A crime scene stain that turned out to be type O blood eliminated roughly half the male population in most US cities. It eliminated almost no one if it was type AB. That was the reality of discriminatory power. Microscopy was the second pillar. Hair and fiber examination took the most time per case because the skill component was enormous. You mounted the fiber or hair on a slide, used both brightfield and darkfield illumination, and compared it against a reference sample under conditions where lighting mattered more than anyone outside the discipline realized. The comparison was subjective in a way that modern DNA work is not. Two examiners could look at the same fiber and reach different conclusions about whether it was consistent with a known sample. Toxicology relied on color tests — Marquis, Mecke, Scott, Froehde — which were fast screening tools, followed by gas chromatography if the lab had the instrument and the budget for columns. Chromatography was not something you ran unless you had confirmation to give, because a single GC run took about forty minutes and required an analyst to sit at the machine the entire time.

Document examination existed as a separate unit in larger labs. Ink dating was mostly guesswork using thin-layer chromatography, and handwriting comparison followed the same subjective framework as hair and fiber. Impression evidence — fingerprint lifting with powder and tape, shoe sole casting with dental stone — was the most procedure-driven part of the work and the least contested in court, largely because the science was simple and the margin for error was visible to anyone paying attention.

How a Case Actually Moved Through the Lab

The intake process was informal by modern standards. A detective would bring evidence in paper bags or brown envelopes, log it into a bound book, and hand it to whatever analyst was free. There was rarely a triage meeting. You opened the package, wrote down what you found, and decided what to run next based on three factors: what the detective claimed happened, what the evidence physically showed, and how long the case had been sitting in police storage before it reached you. Chain of custody was usually a paper trail on the evidence bag and a signature on the intake log. It was not bulletproof, but it was adequate for the volume of cases being processed. The real weakness was contamination control, or the lack of it. Positive control samples sat on open benches. Reagent bottles were uncapped and recapped by whoever grabbed them last. If someone sneezed near an open slide, nobody noticed unless they saw the artifact later and wasted an hour wondering where it came from. The workflow for bloodstain pattern analysis, when it was done at all, consisted of photographs taken with direct flash from about three feet away, rough sketches on graph paper, and verbal descriptions that varied by analyst. Reconstruction was interpretive. The field had no standardized protocol and no statistical framework for how reliably a pattern could be matched to a specific action. That gap is still being filled today.

One thing beginners in this area consistently misunderstand is the relationship between blood grouping and exclusion. Blood typing does not individualize. A match between a crime scene stain and a suspect's blood type narrows the pool, but it does not prove the suspect was present. It proves the blood could have come from them. The courtroom language used by prosecutors and detectives at the time reflected this ambiguity poorly, and it produced wrongful convictions in cases where the jury was never told how little the test actually proved.

A Specific Problem I Ran Into

I worked on a cold case review where the original evidence box contained a set of serology cards from a 1976 homicide. The cards were manufactured on absorbent paper treated with dried reagents, a common format at the time. The cards were brittle from age and humidity damage. When I tried to retest one of them, the paper began to flake at the edges and the reagent layer was already delaminating. The old results recorded in the case file showed a positive reaction to anti-A, but I had no confidence that the card would still deliver a valid result if I added fresh antibody to it. The workaround was to leave the cards intact and instead swab the original stained fabric, which had survived better than the consumables it had been tested on decades earlier. I transferred the stain onto fresh filter paper, eluted the blood in saline, and ran the serology on clean slides with fresh reagents. The confirmed result came back as type O, negative for anti-A. The original positive reading was either a misread weak agglutination or a contaminated reagent from the original testing session. The corrected result excluded the person who had been charged based on the initial finding. That changed the direction of the investigation entirely. The lesson here is practical and unglamorous: old reagent cards degrade. Paper absorbs moisture from the air and the dried antibodies denature over time. If you have the original physical evidence still available, it is almost always more reliable than the consumable the test was performed on. The older the evidence, the more likely the consumable is compromised.

What the Literature Pretended versus What Worked

Textbooks from the era presented forensic disciplines as more definitive than they actually were. Hair comparison textbooks stated that microscopic features could identify a specific individual with high confidence. That claim was overstated. A hair without a root cannot be individualized. Even with a root, nuclear DNA profiling did not exist until the mid-1980s, and mitochondrial DNA sequencing arrived much later. What the microscopist could do was exclude a hair as coming from a particular source, or state that it was consistent with a known sample. Consistency is not identity. The same pattern appeared in toxicology. Color tests were marketed as presumptive identification tools, which they are, but the presumption was too often treated as proof in court. A positive Marquis test suggested an opiate or amphetamine class compound, but it did not distinguish between heroin, morphine, codeine, and a number of synthetic analogs. Confirmation by GC-MS was available in larger labs. Most smaller labs only ran GC without a mass spec detector, which meant retention time matching was the final word, and retention time alone is not definitive for many compounds that co-elute under standard conditions. Another counter-intuitive detail that is rarely mentioned in secondary sources is the role of environmental exposure in degrading evidence before it ever reaches the lab. Bloodstains exposed to sunlight degrade rapidly. UV light breaks down hemoglobin and denatures the antigens that blood typing depends on. A stain that looked promising on a light-colored carpet in a sunlit living room may yield no usable ABO result after six months of exposure, regardless of how carefully it was packaged for transport.

The same degradation issue affected fiber evidence. Synthetic fibers like nylon and polyester are relatively stable, but natural fibers such as wool and cotton lose their cortical structures and surface markings when exposed to heat and humidity. That loss of detail reduces the discriminating power of microscopy to the point where a fiber that might have been class-associated in ideal condition becomes meaningless after decades in a warm storage room.

What Forensic Science In The 1970s Could and Could Not Do

The honest summary is short. Blood typing could exclude a suspect or narrow the pool, sometimes significantly, sometimes barely. Hair and fiber analysis could link or exclude physical evidence to a source, but the conclusions rested heavily on examiner judgment and experience. Toxicology could detect the presence of common drugs and poisons, with confirmation dependent on whether the lab had a functional gas chromatograph. Document examination and fingerprint analysis followed more objective paths, but the quality of the latent print and the condition of the document determined whether anything useful could be extracted. What the era could not do was individualize biological evidence the way modern DNA analysis does. That limitation shaped every conclusion and every verdict. Analysts knew it. Juries did not always know it. Defense attorneys who understood the science used that gap effectively. Prosecutors who did not understand it either overstated the results or failed to disclose the uncertainty, and appellate courts spent decades cleaning up those cases. The practical advice that follows from this is simple and unexciting. If you are reviewing old forensic work, check the chain of custody for gaps, verify the condition of the original evidence rather than trusting the lab report, and apply modern knowledge of contamination and degradation when interpreting results that were never questioned at the time. The science was adequate for what it could do. The problem was almost never the method. The problem was what people believed the method could do.