Question Summary:
If the bird is not slaughtered in the halal way, how can l-cysteine extracted from there can be consumed?

Question Detail:

You answered a question about l-cystine extracted from chicken feather on april 30 2002 fatwa #5471. i want to confirm that if l-cystine is obtained from bird feather in which the bird is not slaughtered in the islamic way then how can the l-cystine from that bird feather be halal to consume. please provide a small amount of detail for convenience.

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
The Darul Iftaa has issued a detailed Fatwa on l-cysteine. You may refer to the following link,
http://askimam.org/public/question_detail/21257
And Allah Ta’āla Knows Best
Bilal Ishaq (Issak)
Student Darul Iftaa
Leicester, England, UK 
Checked and Approved by,
Mufti Ebrahim Desai