And even if it is blood, is it relevant to this investigation?

Is it because someone was injured in this act or is it because it's been there? Is this an artifact that happened before the incident that I'm investigating?

And they have to do their best to get everything right the first time.

The biggest thing with crime scene investigation is the crime scene is a one-way process.

There's no undo button for crime scene investigation.

If something isn't recognized, documented, or collected, it's gone.

You can't go back.