Continuity mistake: After the Hessian, carrying Lady Van Tassel on his horse, jumps back into the tree, her hand is prominently displayed sticking out of the roots. Ichabod faints and it cuts to a wide shot of the entire tree. You can see where the Horseman jumped into the tree but Lady Van Tassel's hand is not there.
Continuity mistake: When Ichabod is being told the history of the Horseman, it shows the Horseman meeting the two Van Tassel children. After the Horseman motions for them to stay silent, young Lady Van Tassel raises the branch that she's holding and snaps it in half. Later, when Lady Van Tassel tells Katrina everything, another flashback seen occurs that shows a young Van Tassel simply breaking the branch without raising it first.
Continuity mistake: At the start of the movie where Ichabod is at the City of New York Municipal Watchhouse there is a medieval device to Ichabod's left, which is open and empty. In the following shot, there is a man standing inside with the doors closed around him.
Answer: As revealed by Lady Van Tassel to Katrina during the film's climax, the midwife Mrs. Killian was abreast of the secrets regarding the affairs of Peter Van Garrett with the widow Winship, as well as their unborn child. Mrs. Killian revealed this secret to Lady Van Tassel right in front of Mr. Killian, which signed both of their death warrants. However, Lady Van Tassel most likely commanded the Headless Horseman to kill the Killians (as opposed to just saying Mr. & Mrs. Killian), to which the Horseman would instinctively murder their child too. It may have been an oversight on the part of Lady Van Tassel, as the child would undoubtedly be ignorant of affairs and the intricacies of legal matters regarding wills, but then again, she probably didn't care anyway.
Phaneron ★