Touch DNA and mixed DNA profiles

Define touch/trace DNA? And what are some sources of this type of DNA?

DNA that is left behind when an object is handled or touched - common sources are cells, sweat and saliva

What factors may affect touch/trace DNA?

Shedder status of the donor, length and force of contact, texture of substrate.

What area/s of a crime scene are usually a good place to find touch/trace DNA?

Entry/exit point

Define direct transfer?

Can occur when someone has touched an item

Define indirect/secondary transfer?

When DNA from someone ends up on an item without them having touched it

what are the 3 circumstances that can lead to secondary transfer?

person to person to object, person to object to person, person to object to object

What 3 factors need to be considered when interpreting DNA mixtures?

How many people, how much did each person contribute, degradation

What 2 uncertainties are we faced with when interpreting mixed DNA profiles?

When is a peak an allele, and whose peak is whose?

What problems arise with confidence on whether a DNA is related to a crime? 3

Cant tell how/when their DNA got there, if the DNA is from an innocent person, and DNA cant be solely relied on in court.