I look forward to reading the research.  I have been personally touched by this subject more times than one should.  I believe every "alleged" suicide needs to be treated as a homicide first and if the law needs to reflect this, let's get it done.  Inquests should be made of those close to the decedent.  It seems to me that declaring a death a "suicide" is made all too easily.  Is that because of lack of training, lack of resources, political pressure, or to just close a case, as long as no one makes a stink about it.  I don't know but can tell you that upon investigating deaths in my family, one should have been ruled an accidental shooting while another was an outright homicide.  I lived with this heartache for three decades before I investigated and came to these conclusions.  I do understand the District Attorneys' Office may not be able to press charges in a homicide without sufficient evidence but when in doubt, don't rule it out.
RIP Yvonne and Elizabeth.