Is this a dagger I see before me?

It may be easier to use a dagger as the murder weapon of book nine of Taylor & Graham.  I am having a heck of a time with my tool of choice.  I thought it would be "fun" to use poison for a change because I've not used that in my books.  So I researched and found what I wanted.  My book of poisons listed it as a toxicity level 5, which is pretty darn potent.  The highest rating is level 6.  Well, the book's fairly old and something whispered in my ear that I better do some further research, as things change.  So I bought a new edition of the same book.  Well, lo and behold!  The toxicity level is now 3 for the same poison!  Which means it's gonna take a lot more of it to do the intended harm.  And I doubt if any sane person who's in the position of my poor victim would come into contact with the needed dose without thinking something's fishy...and not just in Denmark.  I asked my pathologist friend, who supplies me all the medical info in my other books, and she replied that she knows nothing of this element.  So I'm back to wondering if I need to change poisons.  Or change murder method.

I'm rather partial to my original murder method.  I thought it all out and figured out how the poison is to be administered.  Rather cleverly, if I do say so.  If I switch methods to the dagger, let's say, I will have to come up with a whole new scenario for the murder scene.  How will the victim be dispatched now?  What will be his alibi?

It's very hard to commit murder without it being obvious as to whodunit.  At least I think it's hard.  Maybe I can still figure out how to bump off my fellow using the original idea, but I don't want it to wind up being unbelievable.  I could call the poison control center's 800 phone number, but I'm afraid the person answering the phone would think I'm trying to poison someone and this is a nice, easy piece of research.  I do like research, as you may know.  I'm partial to doing things to see how it feels or what my character would do.  But I draw the line at finding police breaking in my door and arresting me for hatching a murder.  A night in jail is just about too realistic for my writing.  I think I'll consider that dagger very seriously....