Something is cooking...

[guohua]

@"BIAD"  You asked.

The question is... where would be the best place to commit this act?

This would depend on the Conscious of the Assassin. Do you care if others are Contaminated?
Do you wish to keep this confined to your Target?
How Reckless, Careless Are You or Just Uncaring?

It also depends too in what form the Poison is in, That would have a lot to do with how he/she or they planned to deliver the Poison. (I'm assuming Jelly Form.) 

After reading your article with the description of the home and surrounding area, An Early Morning or Very Late Night attempt would be good, because you could control the outside environment of the Poison, Door Knob would work then you would quickly come up and with Bleach and Alcohol clean the Door Handle and move off Silently. 

The very best Method and I think would be my choice is his underarm deodorant.  
Gain access into him home and apply a very, very thin coat of the Jelly Poison on the top of his Deodorant.
After he leaves regain access and remove the Deodorant and replace it.
Now you can wait and see if news of his Poisoning makes the news.

But this all depends on your Targets Habits.