A new study in Forensic Science International: Genetics describes the development and evaluation of a 17-plex Hyperplex PCR™ mRNA assay for forensic cell type determination. Identifying the body fluid or cell type behind a stain can strengthen the evidential value of a DNA profile by clarifying how the evidence relates to a specific activity.

Researchers from the National Forensic Centre of the Swedish Police Authority, the Netherlands Forensic Institute and Lund University built the assay with markers for blood, menstrual blood, vaginal mucosa, saliva, nasal secretion and semen. The targets and primer pairs were taken from the established capillary electrophoresis method CellTyper. Single-source samples and mixtures were analysed in two forensic laboratories.

Key results:

• Detection: hpPCR detected all expected markers for semen, blood, saliva, nasal secretion and vaginal secretion. CellTyper gave partial detection for vaginal secretion.

• Comparison: overall, hpPCR gave equivalent or enhanced detection of the expected markers compared to CellTyper.

• Mixtures: hpPCR showed somewhat improved sensitivity for minority contributions of semen and equal detection for vaginal secretion.

• Dynamic range: the large dynamic range removes the need to run several input volumes per sample.

• Flexible input: the assay works with both RNA and cDNA.
  

The authors conclude that hpPCR is a promising alternative to capillary electrophoresis and sequencing for mRNA-based cell type identification. With support for up to 100 targets, the assay can be extended with more mRNA markers and with RNA SNPs to connect the result to an individual.

Read the paper (open access): Sidstedt M, van den Berge M, Sijen T, Hedman J. Hyperplex PCR for forensic mRNA-based cell typing. Forensic Science International: Genetics 87 (2027) 103621. https://doi.org/10.1016/j.fsigen.2026.103621