Non-destructive and simultaneous development and enhancement of latent fingerprints on stainless steel based on the electrochromic effect of electrodeposited manganese oxides.

Latent fingerprints, as one of the most frequently encountered traces in crime scene investigation and also one of the largest sources of forensic evidence, can play a critical role in determining the identity of a person who may be involved in a crime. Due to the invisible characteristic of latent fingerprints, exploring efficient techniques to visualize them (especially the ones resided on metallic surfaces) while retain the biological and chemical information (e.g., touch DNA) has become a multidisciplinary research focus. Herein we reported a new and highly sensitive electrochemical interfacial strategy of simultaneously developing and enhancing latent fingerprints on stainless steel based on synchronous electrodeposition and electrochromism of manganese oxides in a neutral aqueous electrolyte. By utilizing a specially designed device for electrochemical testing and image capture, a series of electrochemical measurements, physical characterization and image analysis have been applied to evaluate the feasibility, development accuracy and enhancement efficacy of the proposed electrochemical system. The qualitative and quantitative analysis on the in situ and ex situ fingerprint images indicates that the three levels of fingerprint features can be precisely developed and effectively enhanced. Forensic DNA typing has also been performed to reveal actual impact of the proposed electrochemical system on subsequent analysis of touch DNA in fingerprint residues. The ratio of detected loci after electrochemical treatment reaches up to 98.5 %, showing non-destructive nature of this fingerprint development and enhancement technique.

Development and validation of a multiplex typing system with 32 Y-STRs for forensic application.

Y-chromosomal short tandem repeats (Y-STRs) with high mutation rates will increase the potential to distinguish related males and improve discrimination capacity. The newly developed Y32 kit is a six-dye multiplex amplification kit that contains 21 rapidly mutating Y-STR loci (DYF387S1a/b, DYF399S1a/b/c, DYF403S1a1/a2/a3/b, DYF404S1a/b, DYS449, DYS518, DYS526a/b, DYS547, DYS570, DYS576, DYS612, DYS626, and DYS627), 8 fast mutating Y-STR loci (DYS458, DYS464a/b/c/d, DYS516, DYS534, and DYS713), and 3 moderately mutating Y-STR loci (Y-GATA-A10, DYS630, and DYS446). To verify the efficiency and accuracy of the Y32 kit, PCR reaction conditions, sensitivity, mixture, concordance, inhibition, species specificity, case samples, reproducibility, sizing precision, stutter, and population study were studied according to the SWGDAM developmental validation guidelines. The results showed that the Y32 kit is efficient, accurate, reliable, and highly informative for forensic applications.

Comparison of Application of MD-VF-Auto SEM Method and Plankton Gene Multiplex PCR System in the Diagnosis of Drowning.

OBJECTIVES: To compare the application effect of microwave digestion - vacuum filtration - automated scanning electron microscopy (MD-VF-Auto SEM) method and plankton gene multiplex PCR system in the diagnosis of drowning. METHODS: Lung, liver and kidney tissue of 10 non-drowning cases and 50 drowning cases were prepared for further MD-VF-Auto SEM method analysis and plankton gene multiplex PCR system analysis. The positive detection rate of the two methods in each tissue was calculated. RESULTS: The positive rate of the MD-VF-Auto SEM method detecting diatoms in drowning cases was 100%, and few diatoms were detected in the liver and kidney tissues of 6 non-drowning cases. By using the plankton gene multiplex PCR system, the diatom positive rate of drowning cases was 84%, and all the non-drowning cases were negative. There were significant differences in the positive rate of the liver, kidney tissues between MD-VF-Auto SEM method and plankton gene multiplex PCR system (P<0.05), as well as the total positive rate of cases. However, no significant differences were found in the positive rates of lung tissues (P>0.05). CONCLUSIONS: MD-VF-Auto SEM method is more sensitive than plankton gene multiplex PCR system in diatom test. But the plankton gene multiplex PCR system can also detect plankton other than diatoms. Combination of the two methods can provide a more reliable basis for the diagnosis of drowning.