The Use of Laser Microdissection in Forensic Sexual Assault Casework: Pros and Cons Compared to Standard Methods

Costa, Samuel Macedo; Correia-de-Sá, Paulo; Porto, Maria João; Cainé, Laura

doi:10.1111/1556-4029.13348

Cited by 17 publications

(4 citation statements)

References 26 publications

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“…Lastly, when compared to its nearest competitor laser-capture microdissection (LMD), or the more recently described DEPArray system, the amount of time necessary to process a mixture sample is shortened dramatically using the optical tweezer method described herein. Sample preparation and optical trapping of 40–60 cells is routinely performed in our laboratory in less than 40 minutes, while the shortest analysis time from sample resuspension to LMD collection on a recent laser-capture microdissection report for a forensic sample was 143 minutes [33]. Once the sexual assault cell sample is added to the cover slip positioned on top of the microscope slide, only approximately 45 minutes is needed to tweeze and collect ca.…”

Section: Discussionmentioning

confidence: 99%

Optical tweezers as an effective tool for spermatozoa isolation from mixed forensic samples

et al. 2019

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A single focus optical tweezer is formed when a laser beam is launched through a high numerical aperture immersion objective. This objective focuses the beam down to a diffraction-limited spot, which creates an optical trap where cells suspended in aqueous solutions can be held fixed. Spermatozoa, an often probative cell type in forensic investigations, can be captured inside this optical trap and dragged one by one across millimeter-length distances in order to create a cluster of cells which can be subsequently drawn up into a capillary for collection. Sperm cells are then ejected onto a sterile cover slip, counted, and transferred to a tube for DNA analysis workflow. The objective of this research was to optimize sperm cell collection for maximum DNA yield, and to determine the number of trapped sperm cells necessary to produce a full STR profile. A varying number of sperm cells from both a single-source semen sample and a mock sexual assault sample were isolated utilizing optical tweezers and processed using conventional STR analysis methods. Results demonstrated that approximately 50 trapped spermatozoa were required to obtain a consistently full DNA profile. A complete, single-source DNA profile was also achieved by isolating sperm cells via optical trapping from a mixture of sperm and vaginal epithelial cells. Based on these results, optical tweezers are a viable option for forensic applications such as separation of mixed populations of cells in forensic evidence.

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Section: Discussionmentioning

confidence: 99%

Optical tweezers as an effective tool for spermatozoa isolation from mixed forensic samples

et al. 2019

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“…Despite these limitations, LMD may be particularly useful in challenging cases whereby small numbers of sperm are present in samples containing large numbers of epithelial cells (Vintiner, Veth, & Bright, 2018). Following staining of the sperm with the Sperm Hy‐Liter Express kit, this technique has been reported to successfully generate high quality genotyping results with only 50 laser microdissected sperm (Costa, Correia‐de‐Sá, Porto, & Cainé, 2017).…”

Section: Isolation Of Male Dna In Sexual Assault Cases—alternatives Amentioning

confidence: 99%

Recent trends and developments in forensic DNA extraction

Chong

Thong

Syn

2020

WIREs Forensic Science

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The extraction of DNA is a fairly standard procedure routinely undertaken in biological academic and research settings. In a forensic DNA context, DNA extraction is the crucial first step toward the generation of DNA profiles used to support convictions or exonerations in the criminal justice system. However, it is often complicated by the additional challenge of yielding sufficient quantities of clean DNA that is free from environmental inhibitors, from a wide spectrum of sample types which may contain limited quantities of biological material. While improvements in methods and technology over the decades have sped up and simplified the process of DNA extraction, several issues remain to be fully addressed—such as the incomplete separation of spermic DNA from sperm‐epithelial cell mixtures, increasing demands for ever‐faster DNA results, or even on‐scene DNA processing, and processing of difficult samples such as skeletal remains or samples contaminated by Chemical, Biological, or Radiological (CBR) agents. These challenges are often compounded by high work volumes and limited quantities of starting material. As such, this review focuses on recent trends and developments in four areas of forensic DNA extraction: (a) analysis of sexual assault evidence which often represents a significant portion of a forensic DNA laboratory's casework, (b) use of portable rapid DNA instruments which has gained much traction among law enforcement in recent times, (c) DNA extraction from difficult and CBR‐contaminated samples which, albeit rare, would be essential in a DNA laboratory's toolbox in the event of an incident, and (d) bypassing DNA extraction altogether. This article is categorized under: Forensic Biology > Forensic DNA Technologies

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“…Male DNA typing has been done from 25‐year‐old vaginal swabs . The use of laser microdissection with fluorescence also may be useful in capturing male cells .…”

Section: Discussionmentioning

confidence: 99%

Cold Case Homicides: DNA Testing of Retained Autopsy Sexual Assault Smears

Clark

Gill

Sasinouski³

et al. 2019

Journal of Forensic Sciences

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Archival medical examiner specimens may contain perpetrator DNA evidence useful in unsolved (“cold case”) homicides. The Office of the Chief Medical Examiner (OCME) histology slide archives were searched for sexual assault smears for all 376 female homicides from 1990 to 1999. Of these, the OCME had sexual assault smears on 84 of which 13 slides had sperm. Of these 13, six were still unsolved. DNA profiles were obtained on all six (5 from smears and one from swabs). Combined DNA Index System ( submission resulted in two matches (“hits”) for new suspects. In addition, three suspects were eliminated in two cases. Our review of archival sexual assault smears resulted in DNA profiles that were able to assist in the investigation of four cold case homicide investigations. It may be worthwhile for medical examiner offices to search their archival histology slides for sexual assault smears on previously unsolved cases particularly those prior to the mid‐1990s when DNA testing was less widely available.

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The Use of Laser Microdissection in Forensic Sexual Assault Casework: Pros and Cons Compared to Standard Methods

Cited by 17 publications

References 26 publications

Optical tweezers as an effective tool for spermatozoa isolation from mixed forensic samples

Optical tweezers as an effective tool for spermatozoa isolation from mixed forensic samples

Recent trends and developments in forensic DNA extraction

Cold Case Homicides: DNA Testing of Retained Autopsy Sexual Assault Smears

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