How Scientists Can Tell How Old a Blood Stain Is

Investigating animal cruelty can be tough, especially when it's unclear how long a blood sample has been at a crime scene. This is where the concept of time-since-deposition (TSD) comes into play. Scientists have been working on a new method to estimate the age of canine blood samples. The idea is to look at changes in the autofluorescence of cells over time. Autofluorescence is a natural glow that cells emit when excited by light. By measuring this glow in two specific channels, researchers found they could tell the difference between older and newer blood samples. Older samples, like those that are 6 months or a year old, showed different autofluorescence patterns compared to newer ones, which are less than three months old.The study also found a strong link between autofluorescence and time for samples aged between one day and three months. This means the older the sample, the more its autofluorescence changes. The researchers even created a model to predict the age of blood samples. This model was tested on mock crime scene samples and showed some errors, but it was pretty accurate, especially for samples less than 6 days old. This new method could be a game-changer for animal cruelty investigations. It can help investigators prioritize blood samples based on their age, making it easier to focus on the most relevant evidence. This is particularly useful in cases like illegal dog fighting or individual injuries. However, it's important to note that this method is still being developed. While it shows promise, more research is needed to improve its accuracy and reliability. For now, it's a step in the right direction for animal cruelty investigations.