Forensic Sciences 2020

The necrobiome is the community of organisms that use or are affected by decomposing organic matter.  Decomposing organic matter comes in the form of dead plant matter (biomass) or that of dead animals, including humans.  Using research into how these communities (e.g., insects, pollen, microbes) colonize, use and change during the decomposition of vertebrate carcasses can inform science with potential forensic utility. One emerging area of forensic research has been into postmortem microbiomes and how they have potential to estimate postmortem intervals, postmortem submersion intervals, manner/cause of death and other areas of investigative interest. While recent research on postmortem microbiomes shows excellent promise, there are several challenges that will limit practical use during death investigations; these issues span from basic experimental desing and context to understanding the extent of variability in postmortem microbiomes across human demographics, ethics, geography and time.  This presentation provides an introduction to the necrobiome commonly associated with decomposing animals, including humans; a summary of past and current research into postmortem microbiome science; example case studies; and a discussion of the challenges that will require consideration and solutions before postmortem microbiome evidence becomes acceptable and used within the forensic sciences.

Learning Objectives

1. Define the postmortem microbiome and two examples of how it can be potentially used in forensic sciences.
2. Identify various challenges in using the postmortem microbiome in forensics.
3. Describe the pros and cons of performing research in anthropological research facilities versus autopsies (or cases) to provide postmortem microbiome data that can be used in future routine death investigation.

The ever-increasing number of deaths along the U.S.-México border and the diversification in the demographic characteristics of the Latin American migrants, who perish in this region, demand new approaches to forensic anthropological casework. Current rates of positive identification must be improved so that the unknown forensic case can be re-associated with the once living person, the individual’s remains returned to the family, and the needs of social justice can be served. Studies using genetic and skeletal data alike have revealed differences in ancestry for many of the spatially-defined groups that are distributed across Latin America. Demographic research on migration networks for México have found distinctive transit pathways El Norte, whereby migrants of different origins are associated with particular destinations across the U.S.-México border. In this presentation, I will argue for the value of extending these two lines of research on the living to the identification of the dead for methodological improvement in the forensic context. Specifically, I will show how, when combined, information on geographic variation in ancestry composition and spatial trends in migration are critical to building statistical models optimized for the probabilistic determination of personal identity for migrant fatalities recovered along our southern border. By quantifying these biogeographic patterns in terms of the unknown individual’s relative estimates of continental-level ancestry, geographic location of origin, and place of death along the border, I will demonstrate that it is possible to predict the individual’s sending region. Through this discussion, I will illustrate how geospatial and machine learning methods can be used to improve traditional forensic procedures by directing case investigation, providing probable locations for finding next of kin, and reducing the pool of potential matches from missing persons lists. In conclusion, I will advocate for adopting a bio-cultural approach to identification that leverages multi-disciplinary methods to aid in this human rights work.

Learning Objectives:

1. Introduce the concept of biogeography and explain its value as an alternative biological profile parameter to single-group ancestry

2. Demonstrate how novel geospatial and machine learning methods can be used to infer place of origin for unknown remains

3. Explain how trihybrid ancestry estimates can be generated from skeletal data using admixture algorithms comparable to those employed in forensic genetics

The potential for cognitive bias in forensic evidence interpretation and crime scene investigation continues to receive attention and debate within forensic and academic communities. Starting with just a few studies in the early 2000s, cognitive bias has now been examined in nearly every forensic discipline and is a dedicated topic within many scientific committees and working groups around the world. This presentation will track the progression of cognitive bias studies and their influence on forensic science practice, as well as highlighting the challenges inherent in designing and carrying out such research. We will also examine the benefits to implementing contextual information management, and how rethinking the role of contextual information in forensic decision-making facilitates some much-needed discussion about the true nature of scientific reasoning in forensic science.

This will be an interactive presentation. Please bring a pen and paper and play along as we challenge some of our own biases!

Learning Objectives:

1. Identify the challenges inherent in cognitive bias research as it relates to forensic evidence interpretation

2. Understand the difference between “bias” and the “application of task-relevant contextual information.”

3. Recognize the value of contextual information management procedures, regardless of the outcome of cognitive bias studies.

Microhaplotypes (microhaps) are biomarkers less than 300 nucleotides long that display multiple allelic combinations. The main advantages of microhaps over conventional short tandem repeats (STRs) include the absence of stutter, same-size alleles within each locus, lower mutation rate, and ancestry informative alleles. These forensically relevant loci can yield a power of discrimination similar to STRs while enhancing human identification (HID), mixture deconvolution and biogeographic ancestry prediction. Sanger sequencing does not allow determining the cis/trans relationship among closely related SNPs while massively parallel sequencing (MPS) allows determining the parental haplotypes at each locus by clonally sequencing of each DNA molecule if they are included in the same amplicon. Currently, STR panels are used for mixture deconvolution and SNP assays are used for ancestry inference. Microhaplotypes can be used for both functions allowing, for example, to infer the ancestry of a minor contributor to a mixture (DNA intelligence). In this presentation we discuss the current status of the research conducted in the GW-FMB lab on this new multi-function DNA marker and its potential impact to the field of in forensic genetics.

Learning Objectives:

1. Molecular basis of microhaplotypes

2. Informativeness and power of discrimination of microhaplotypes

3. Mixture deconvolution via microhaplotypes

The current standard methodology in forensic DNA typing relies on amplification of short tandem repeat (STR) markers by the polymerase chain reaction (PCR) and allele sizes (i.e., length-based) determined for each locus using capillary electrophoresis (CE). Massively parallel sequencing (MPS), also known as next generation sequencing (NGS), allows high throughput sequencing of STR amplicons, which can identify nominal length-based (LB) genetic variation but equally as well inter-allelic sequence (sequence-based; SB) variation. The increased effective number of alleles per marker for some STR loci improves discrimination power, which may be invaluable in some cases of kinship analysis and for mixture de- convolution. Furthermore, allelic variation captured using MPS may be useful towards understanding of STR mutations and their rates and may contribute to evolutionary studies using STR markers. One issue with current massively parallel sequencing (MPS) is the need to capture flanking region sequence variation to exploit the full power of forensically relevant STR loci. The application of such data will increase our knowledge and understanding of each locus, gain additional genetic information about population specific genetic parameters, increase the power of discrimination of a locus, and potentially aid in mixture de-convolution efforts. The underlying genetic variation needs to be described through studies on various population groups.

Learning Objectives:

1. Understand the advances in sequence-based technologies in Forensic DNA typing

2. Understand the major commonalities and differences between current and futuristic DNA typing methods

3. Acknowledge the complexities of the human genome for forensic human identity applications