The identification of human body fluids or tissues through mRNA-based profiling 
is very useful for forensic investigations. Previous studies have shown mRNA 
biomarkers are effective to identify the origin of biological samples. In this 
study, we selected 16 tissue specific biomarkers to evaluate their specificities 
and sensitivities for human body fluids and tissues identification, including 
porphobilinogen deaminase (PBGD), hemoglobin beta (HBB) and Glycophorin A (GLY) 
for circulatory blood, protamine 2 (PRM2) and transglutaminase 4 (TGM4) for 
semen, mucin 4 (MUC4) and human beta defensin 1(HBD1) for vaginal secretion, 
matrix metalloproteinases 7 and 11 (MMP7 and MMP11) for menstrual blood, keratin 
4(KRT4) for oral mucosa, loricrin (LOR) and cystatin 6 (CST6) for skin, histatin 
3(HTN3) for saliva, statherin (STATH) for nasal secretion, dermcidin (DCD) for 
sweat and uromodulin (UMOD) for urine. The above mentioned ten common forensic 
body fluids or tissues were used in the evaluation. Based on the evaluation, a 
reverse transcription (RT) PCR multiplex assay, XCYR1, which includes 12 
biomarkers (i.e., HBB, GLY, HTN3, PRM2, KRT4, MMP11, MUC4, DCD, UMOD, MMP7, 
TGM4, and STATH) and 2 housekeeping genes [i.e., glyceraldehyde-3-phosphate 
dehydrogenase (GAPDH) and 18SrRNA], was developed. This assay was further 
validated with real casework samples and mock samples (with both single source 
and mixture) and it was approved that XCYR1 is effective to identify common body 
fluids or tissues (i.e., circulatory blood, saliva, semen, vaginal secretion, 
menstrual blood, oral mucosa, nasal secretion, sweat and urine) in forensic 
casework samples.