The lawyer was not sure
The lawyer was aware that Patricia and Mark had lived in the home for about a decade. The timeline was therefore crucial. The age of the object was a mystery to him.
Mark understood the seriousness of the situation. If the team could collect evidence that the strange metal artifact had been buried in that location around when Mark and Patricia moved in, then the scales would tip against him. He was in grave danger. The timeline was critical to the case and stakes were very high.
