Jerome Hart's clan hailed from a lineage of traditional Chinese medicine practitioners, their greatest expertise being the Silver Needle Techniques. It could be said that David Hart was the most authoritative in the way of the Silver Needle, and Jerome had fully inherited David's skills.
He explained in detail the method of needling, the depth required, and so on. Although the process was simple, it was also very complex. Too deep wouldn't do, and neither would too shallow.
Yusuf Zuck was bound to seek revenge. Since his adversary was too powerful, a blatant retaliation would only attract bigger trouble. Hence, the Lethal Needle could solve many problems.