The prosecutors analagy was so good. Circumstantial is just as solid as direct, sometimes more solid. Direct can even leave questions.. let's say there is DNA.. well Alex lives there.. there would be DNA so does that make it easier to say he did it? No probably not.
They used the rain analogy. If you hear thunder and rain on your roof, but don't see rain because you are inside, but then you go outside an hour later and it's not raining, but everything is wet then you can reasonably conclude that it rained. He said sure the neighbor could have taken a hose and sprayed the entire area down with water, but what is more likely?
So let's say several circumstantial things are at play, but all would suggest one specific narrative.. that is powerful when compared to say DNA or a fingerprint being found because those things would be expected to be on a property owned by the defendent.