A new test can spot blood at crime scenes by reading tiny RNA markers.  

Instead of looking only for DNA, investigators now check the mix of body fluids.  

Scientists chose 14 single‑nucleotide changes in four blood‑specific genes: CD3G, ANK1, SPTB and GYPA.  

The test uses a one‑step method that first copies the RNA into DNA, then reads the 14 spots in a single run.  

It works on very small amounts of material—just one nanogram of total RNA is enough.  

When the team ran the assay on single blood samples and mixed stains, it correctly identified all of them.  

Only a few of the markers appeared at low levels in menstrual blood and vaginal secretions, so those fluids can be told apart too.  

To confirm the test’s accuracy, 19 blood samples were typed both by DNA and by RNA.  

Every result matched perfectly, showing the method is reliable.  

The researchers also checked how well the 14 markers can separate people.  

Using data from 100 unrelated Han Chinese men and women, the combined power to distinguish individuals was 0. 98303—almost certain.  

Overall, this quick and sensitive test gives forensic teams a powerful tool to read blood evidence and separate mixed stains.


# A New RNA Test Spotlights Blood at Crime Scenes

A breakthrough assay now reads **tiny RNA markers** to identify blood, expanding forensic analysis beyond DNA alone.

## How It Works

- **Target Genes**: Four blood‑specific genes—`CD3G`, `ANK1`, `SPTB`, and `GYPA`.
- **Markers**: 14 single‑nucleotide changes selected for high specificity.
- **One‑Step Protocol**:
  1. Convert RNA to DNA (cDNA).
  2. Sequence all 14 spots in a single run.

## Sensitivity & Accuracy

- Requires only **1 ng of total RNA**.
- Tested on isolated blood and mixed stains—*all samples identified correctly*.
- Minor cross‑reactivity with menstrual blood and vaginal secretions, but distinct enough for separation.

## Validation

- **19 samples** typed by both DNA and RNA—*100 % concordance*.
- Population study with 100 unrelated Han Chinese individuals:
  - **Combined discriminatory power**: `0.98303` (almost certain individualization).

## Impact

This rapid, sensitive test equips forensic teams with a powerful tool to detect and analyze blood evidence, even in complex mixed‑stain scenarios.



Blood Clues Decoded with a 14‑Gene Test

How It Works

Sensitivity & Accuracy

Validation

Impact

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