The scenario is this: the husband is severely ill & bedridden unable to get up or do anything himself so he depends on his wife being the caretaker. However, her intentions are far from good since all she’s after is his estate (so she feeds him with a catch: by poisoning his food and beverage as the toxin slowly kills him so she can claim his estate).

The poison he’s being fed mimics his pre-existing condition which makes it hard to tell if its the toxin in his body or the sickness doing it. Later, he passed away (from what is apparently his illness but toxicology indicates that his system has high traces of a certain chemical which doesn’t add up from someone who died whilst lying bedridden).

Her motive for the crime is simple: she wants his estate (money & assets) to live off his wealth. She took advantage of her spouses illness in the sense of using his immobility to fend for himself while poisoning him. Traces of the poison are found on the victim’s system, so what? How would you prove she intentionally murdered her husband with that?

To prove she had the intent on murdering her husband for his estate when confronted in trial:

• What occupation does she have to access those kinds of substances?
• CCTV footage shown where she acquired or purchased the chemical
• Bank statements indicating if she paid for the chemical using her card
• Eyewitnesses (guests) may’ve seen a strange chemical no housewife owns
• Analyze all contaminated foods (left overs) he last ate to detect the poison
• Looking through trash to find “if” the bottle containing the poison is still there
• Her fingerprints must be found on the poison bottle (meaning she handled it)
• Traces must be found on cutlery, plates and cups the victim used before death

The bottom latter half mentioned above might be hard to come by as “raw” evidence since she might have washed the dishes eroding all evidence of her crime or the trash she threw out has already been collected by the garbage man (with the bottle) and the possibility she used gloves to handle the bottle of poison whilst spiking his food & beverages.

The fourth point mentions about possible eyewitnesses (during parties) who saw something unusual for a housewife to have in a kitchen (i.e. industrial grade chemicals, the ones used by tradesmen and absolutely toxic for humans) but their concerns can be dismissed if they knew her occupation is a scientist, chemist or tradeswoman beforehand.

However, if she’s not employed in any of those fields: then why would a housewife keep something like that in the kitchen? Since highly poisonous substances can’t be purchased at a “normal” store (only specialized chemical companies or labs possess such) meaning she might known whom to connect with to acquire the poison.

If that were the case: they are also eyewitnesses in the sense of recognizing her as a client who bought the poison from them or accomplices since they indirectly gave a potential murder weapon without knowing her intention behind what she’ll do with it (as they failed to question her as to why she needed that before proceeding with the transaction).

If relatives came to his bedroom not seeing him get any better or relief after a long time, then possible signs of his wife by not contacting emergency services immediately as he’s not abled bodied to so do on his own, neglecting her duty on taking care on a sick person or withholding his wish from being referred to professional caretakers.

Or that relatives overheard his last words saying: “This tastes funny” (implying she tampered with his food) but not suspected yet until the toxicology report confirms there’s a high amount of (substance) that’s harmful to humans which is not typical of someone bedridden to die from (like high arsenic or lead content in his system, which is toxic).