1. I can't find any links to the lake story.
2. I can't find any links to the Matamoris Mexico story.
3. The PBS site specifies that over 270 women (many of them prostitutes) have been raped and murdered. The El Paso Times mentions nothing about ritual killings, only mentioning the possible activity of a serial killer or killers.
Satanic ritual abuse in the UK was investigated in a Government-commissioned report by Jean LaFontaine; I was there when she presented it at a meeting in Central London in the Nineties. She examined 84 cases, following the Orkneys and Nottingham cases. 81 had no 'Satanic' ritualistic elements of abuse. 3 were borderline; one guy claimed he was Satan himself, another claimed the Virgin Mary told him to do it. No mention of specific dates. The 3rd case bore no relation to any known occult beliefs or practices. There is also the element of 'false memory syndrome' to be accounted for, which has been promoted by some psychotherapists and Christian fundamentalists ever since the publication of 'Michelle Remembers' in 1980. Other authors such as Rebecca Brown, Audrey Harper and Doreen Irvine have jumped on the bandwagon, but the police have found no evidence at all that there is a criminal case to be investigated. In all three cases, the authors had known involvement with drugs which I believe caused them to hallucinate.
One case which may have been a Muti killing is that of the 'Adam' torso discovered in the Thames. Police are still investigating that one. If there is a link at all to any 'spiritual' beliefs, it will be to West African traditional religion.
I have yet to see evidence that inextricably links human sacrifice to Satanism or Western Paganism, particularly in connection with Halloween. I will be willing to explore any links you can provide.
Jules