Final answer:
In a decapitation case, the upper end of a dowel attached to the torso is likely inserted into the axis second cervical (C2) vertebra, which serves as the pivot for the skull.
Step-by-step explanation:
In the context of a decapitation case, the mention of a dowel being attached to the torso likely refers to a procedural aspect of an autopsy or a reconstruction technique in forensic anthropology or medicine. When considering anatomical structures, the upper end of a dowel attached to the torso for reconstructive purposes or support could be inserted into the axis second cervical (C2) vertebra. This makes sense as the axis is the vertebra that forms the pivot upon which the first cervical vertebra (the atlas), which supports the skull, rotates.
The brain case, or the portion of the skull that contains and protects the brain, would have originally been supported by the cervical vertebrae, including the atlas and axis, before decapitation. The mention of the head of the femur and neck of the radius in the reference material, although related to the appendicular skeleton, are not directly relevant to the question about the upper end of a dowel being inserted into the neck area after decapitation.