Teichmann and Takayama Crystal Tests

Ludwig Teichmann, working in Krakow in the 1850s, found that when dried blood is treated with a chloride salt and glacial acetic acid under gentle heat, the haem group oxidises and incorporates the halide to form haemin (ferriprotoporphyrin IX chloride). The crystals that grow are small (roughly 10-40 micrometres), brown, rhomboid in shape, and often cluster in pairs or small groups. Under low-power microscopy their outline is unmistakable to a trained analyst.

The standard reagent preparation is straightforward. A small scraping from the dried stain is placed on a glass slide and a few grains of sodium (or potassium) chloride are added along with a drop of glacial acetic acid. A cover slip is placed on top and the slide is gently heated over a low flame just until the liquid begins to simmer at the edges. After it cools, the slide is examined at 100-200x magnification for rhomboid brown crystals.

The test is considered positive only when the analyst observes crystals of the correct shape and colour. A brownish smear or amorphous precipitate is not a positive. This morphological criterion is what gives the Teichmann test its specificity: other substances may react with acetic acid, but they do not produce haemin rhombs.

Masao Takayama published the pyridine haemochromogen test in 1912. The chemistry is the opposite polarity to Teichmann: instead of oxidising the haem iron, the Takayama reagent reduces it and coordinates a nitrogen-containing base (pyridine) to the central iron. The product, pyridine ferroprotoporphyrin, crystallises as pink or salmon-coloured needles or feathery clusters. The typical crystal is elongated, pointed, and a few tens of micrometres long, quite distinct from the brown rhombs of Teichmann.

The Takayama reagent consists of pyridine, glucose (the reducing agent), sodium hydroxide (to create an alkaline medium), and water. A few drops are placed over the dried stain scraping on a microscope slide; the slide is gently warmed, and crystals are sought after cooling. The pink haemochromogen crystals are visually distinct under the microscope. False crystal morphologies, such as sodium hydroxide precipitates, are colourless or white, so colour also helps discriminate.

Both crystal tests depend on intact haem. Haemoglobin degrades over time as the globin protein denatures and the haem group oxidises further or breaks down. The rate depends on temperature, humidity, UV exposure, and whether the stain was mixed with soil or other materials. A bloodstain dried on fabric and stored away from light can remain reactive to crystal tests for years. A stain exposed to repeated wetting and heat may fail after months.

Comparative studies have consistently shown the Takayama test to have a slight sensitivity advantage on degraded samples. This is thought to be because the reduction-based haemochromogen reaction can work with a somewhat greater degree of haem oxidation than the Teichmann oxidation step requires. In practice, when a stain fails to produce Teichmann crystals, the analyst should attempt the Takayama test before concluding the sample is non-bloodstaining.

Analysts should also be aware that certain substances encountered at crime scenes can interfere with crystal formation. High concentrations of rust (iron oxide) can partially suppress haemin crystal growth. Chemical bleach breaks down haem porphyrins and will prevent crystallisation even when a large amount of blood was originally present. When bleach contamination is suspected, the negative crystal result does not rule out the prior presence of blood.

Both the Teichmann and Takayama tests are specific for haem-containing blood. They will not react to coffee, rust water, fruit juice, or most plant pigments because none of those contain haem. This is a meaningful advantage over screening tests like luminol or phenolphthalein, which can be triggered by peroxidases found in plants and certain metals. The crystal test is a confirmatory step precisely because of this specificity.

• Blood species: haemin and haemochromogen form from the haem group, which is structurally conserved across mammals. The crystals from human blood and dog blood look the same. Species identification is a separate test.
• Individual identification: crystal tests give no information about the individual. DNA typing or blood group serology is required for that.
• Age of the stain: the tests cannot reliably date a stain. A positive means blood was present, not when it was deposited.
• Menstrual vs traumatic blood: the tests do not distinguish source tissue. Both produce the same crystal because both contain haem.

In practical casework, crystal tests are used when the analyst wants a chemical confirmatory result that does not depend on antibody reagent supply or kit shelf life. They are also sometimes used as a corroborating second confirmatory test alongside a lateral-flow immunoassay, particularly in cases where the result will be challenged in court and independent lines of evidence are desirable.

A forensic scientist reporting a Teichmann or Takayama result states: the test was performed, the crystals of the appropriate morphology were observed (or not observed), and therefore the substance is (or is not) confirmed as blood. The report does not overstate this. Confirmed as blood means the haem chemistry is present. It does not mean the blood is human, it does not say whose blood, and it does not say when it got there.

Documentation typically includes a photomicrograph of the crystals taken through the microscope eyepiece. This image becomes part of the case file and can be reviewed by a defence expert. Courts in multiple jurisdictions have accepted photomicrographic evidence of haemin and haemochromogen crystals as confirmatory of blood for well over a century, and the long history of the tests supports rather than undermines their evidential standing.

A well-equipped laboratory will run both tests when the sample allows, because two independent positive crystal results are stronger than one. When sample volume forces a choice, the decision turns on the condition of the stain. Fresh or recent stains on clean fabric: either test works, and the Teichmann has a longer history and simpler reagent shelf life. Old stains, degraded material, or any sample where the Teichmann produces atypical crystals: attempt the Takayama first or as a follow-up, given its reported sensitivity advantage.

Reagent preparation and shelf life also matter in the field. Glacial acetic acid for the Teichmann test is stable almost indefinitely when stored correctly. The Takayama reagent containing pyridine and glucose has a shorter working life once mixed and should be prepared fresh or checked for efficacy before use on a critical sample. A failed Takayama from a degraded reagent looks exactly like a failed Takayama from absent blood, which is an important quality-control consideration.