Non-human DNA Forensics

Non-human DNA Forensics

Introduction

Non-human DNA analysis in forensic science has gained very rapid growth in recent years. It has applications range from investigations of rape and murder of humans to cruelty and poaching in animal/wildlife species. DNA evidence from bacteria, animals, plants and viruses has been used in criminal investigations. When there is an absence of biological evidence to directly relate a suspect’s DNA to a victim or crime scene, the facility to employ non-human DNA found as trace evidence at a crime scene to indirectly make this connection is a highly useful one. With human DNA profiling, individualization is most commonly endeavoured using STR genotyping. In some cases where STR profiling is challenging due to the lack of sufficient amounts of nuclear DNA, mitochondrial DNA (mtDNA), being more robust to degradation and available in larger copy numbers, has been effectively evaluated. In most of the animals, the 50 HVR region of the control region or D-loop is ordinarily sequenced, and nowadays a number of databases are present in domestic species for mtDNA haplotype frequencies. But like humans, there are limitations in using mtDNAas it is not suitable for positive individual identification. Additionally, its exclusion capacity is lower than that seen with STR loci. This problem is further deepened in domestic animals such as dogs and cats, which have far higher frequencies of common haplotypes and far fewer haplotypes than humans.

Types of non-human biological evidence

In addition to hair, other biological material found as trace evidence has been used efficaciously in forensic investigations e.g. DNA from saliva around bite wound or bitten material, DNA from faeces and urine of dogs and DNA from plant and soil evidence.

Types of investigations

Analysis of soil DNA

Identification of soil gathered as trace evidence can provide important hints leading to settlement of a case. Having an extremely complex matrix, soil characterisation is often carried out using DNA profiling of bacterial groups in the soil which uses the length hypervariability of 16s ribosomal RNA domains and the generated met genomic profiles are then compared between regions.

Analysis of viral DNA

In a criminal case State of Louisiana v. Dr. Richard Schmidt, 1998 in the USA, Dr Schmidt, a gastroenterologist, who had an extramarital affair with his nurse Ms Trahan for years, was suspected of her attempted murder. It was assumed that when their relationship was ended by Ms Trahan, Dr Schmidt injected Ms Trahan with blood from one of his HIV-positive patients. After having cleared other possibilities of infection, in order to ascertain that Ms Trahan had been infected by  Dr Schmidt’s patient, sequences of two HIV genes were acquired from both individuals and equated to other HIV patients in the local area. Phylogenetic analysis was performed. A close relationship between the HIV sequences of Dr Schmidt’s patient and Ms Trahan was discovered, and those sequences from the local population sample were much more distant. This characterized first time that Dr Schmidt was convicted of attempted murder by using phylogenetic analyses in a criminal court case.

Drug enforcement

In drug prosecution cases, it is often problematic to recognize controlled substances, particularly when drugs are dried or powdered. Tsai et al. has effectively used DNA sequencing of the ribosomal internal transcribed spacer regions, ITS 1 and ITS 2, in the nuclear genome and the trnL-trnFintergenic spacer region in the chloroplast genome toidentify Cannabis concealed as lawfully imported plant products in Taiwan. Since Cannabisplants can be propagated either clonally by taking cuttings or from seed, DNA approaches competent to discriminate between the two can support investigations into finding sources of Cannabis growers and linking suspects to individual growing operations.

Analysis of animal STR DNA

The first known use of animal DNA evidence in a criminal investigation was in Canada in 1994. When the RCMP (Royal Canadian Mounted Police) found the dead body of Shirley Duguay who had been missing for 8 months from Prince Edward Island, they suspected that Douglas Beamish, her former husband, was involved in her murder. A blood stained leather jacket was found near Ms. Duguay’s body, which was supposed to belong to Beamish. Although blood on the jacket was matched to match Ms. Duguay’s, an identification of the jacket’s ownership remained difficult.Forensic scientists found a small number of white hairs of a cat on the jacket. Beamish, living with his parents, owned a white cat called Snowball.Investigators took a blood sample from Snowball and referred it for DNA testing along with the hair from the jacket. The outcomes exposed that 10 dinucleotide STR loci had the similar alleles in both the DNA from the DNA recovered from the root of one hair found on the jacket and Snowball’s blood. This evidence connected Beamish in Ms. Duguay’s murder and he was later imprisoned.

Analysis of animal mtDNA

For dogs, a number of mtDNA control region haplotype frequency databases have been testified in various countries e.g. Japan, USA,Sweden, Belgium,UK with sequences ranging in length from 580 bp– 1,4000 bp (complete) in length. Some haplotypes are found to be common in dog populations and other rare haplotypes are supposed to be important in terms of evidentiary value. State of California v. David

Westerfield, 2002 was first criminal case where inadequate DNA prevented STR analysis and compelled the use of mtDNA. When STR implication was ineffective, the mtDNA control region was used for implification and sequencing and a match was obtained between dog hair obtained from crime scene and Van Dam’s dog hair. The frequency of the haplotype was assessed at 9% (Questgen Forensics). This was used as proof in court and David Westerfield was convicted of Danielle’s kidnap followed by murder and sentenced to death.

 Dog/bear attack

In some cases where humans are pounced on by dogs, DNA evidence are obtained from saliva around the bite wound and used to bring the owners of a brutal dog to justice.Frosch et al. reported in a rare case of a fatal attack of a human by a bear in Europe that the wrong bear had been shot by officials in Bulgaria. They used 12 STRs on bear hair collected from the scene of the attack and hair/tissue from the carcass of a shot bear to reveal this wrong action of management.

 Plant DNA

The use of plants as evidence in criminal investigations is called Forensic botany.It comprises a number of spheres including, plant anatomy, plant systematic and palynology (pollen analysis). During the commission of crimes happened outdoor, plant material may be transferred from the crime scene to the perpetrators or victim. This plant material may help in be probation due to the individual genotype identified or restricted geographical distribution of the plant species. The major experimental tool of the forensic botanist remains the light microscope but the intra-species genetic variation is best decided by molecular genetics methods.

The very first reported application of plant DNA evidence reminds the molecular identification of seed pods from a Palo Verde tree used to relate a suspect to a precise crime scene. An Arizonan geneticist

designed multiple primer RAPD analysis and then was able to reveal inter-individual variation among diverse Palo Verde trees. The suspect was imprisoned.

Patent infringement

In a patent violation case, Congiu et al. confirmed using RAPDs that a patented variety of economically important strawberry (Marmolada) had been unlawfully commercialised by farmers in Italy. The RAPD results showed banding patterns in 13 of the 31 plants tested that were alike the Marmolada variety. This confirmation was used in court against the farmers.

Other

In the Cessna aircraft crash investigation in Oklahoma in 2008, Dove et al. used COI DNA sequencing on feathers procured from the engine in order to recognize the species of bird responsible for the crash. In a case of suspected suicidal poisoning of a 23-year-old female student, her body was found beside green vomit and red berries, an autopsy showed presence of partially crushed yew leaves in the stomach. Gausterer et al. confirmed presence of Taxus spp. in the stored gut contents using ribosomal ITS 1 DNA sequencing, providing evidence for suicidal poisoning.

 Prospective

The prospective offered by the application of non-human DNA in solving crime cases is clearly gigantic. An enormous range of crimes has productively been solved using nonhuman DNA from varied species. Forensic laboratories normally necessitate accreditation for quality assurance purposes and this is an expensive process and unfeasible to acquire for many low-scale laboratories.