I thought it was brain spatter.

Source: https://www.fitsnews.com/2023/02/23/murdaugh-murders-trial-alex-murdaugh-takes-the-stand/?utm_source=rss&utm_medium=rss&utm_campaign=murdaugh-murders-trial-alex-murdaugh-takes-the-stand

Murdaugh's defense lawyers filed another motion this morning seeking to ensure state prosecutors can't introduce high-impact blood spatter as evidence in the upcoming trial.

Source: https://www.postandcourier.com/murdaugh-updates/alex-murdaugh-double-murder-trial-begins-with-jury-selection/article_2549eefa-9771-11ed-bc8a-f3aec581a6ac.html

Prosecutors claim that at least some of the blood is high-velocity impact spatter from one or both of the victims.

Source: https://www.theguardian.com/us-news/2023/jan/21/alex-murdaugh-trial-family-murders-south-carolina

Prosecutors say that blood spatter was found on the shirt that Mr Murdaugh was wearing on the night of the murders.

Source: https://www.independent.co.uk/news/world/americas/crime/alex-murdaugh-story-murder-trial-b2269235.html

She also said she was not aware of media reports referencing the purported blood spatter.

Source: https://www.independent.co.uk/news/world/americas/crime/alex-murdaugh-testify-murder-trial-b2282030.html