I found an 1881 civil death index record for a William Mullen in the Rathdrum registration district which includes Rathnew civil parish. Possibly this is your relative.You can get a copy of the record from the General Register Office for approximately 4 euros.The record will show the location of death, cause of death and the name of the informant. Instructions for getting a copy are below.
Go to this link http://www.welfare.ie/en/Pages/Apply-for-Certificates.aspx In the middle of the page there are links for birth, marriage or death certificates. Hit the link for the form you want. You will likely get a screen asking for a User Name and Password. (This is a program bug that the GRO has to correct). Hit cancel and the appropriate form should come up. Print the form and complete the requested information. Also provide the information from the index record--quarter/year of the event. registration district and the volume and page number where the event is recorded. Make sure you ask for a copy which costs around 4 euros. ( A cert costs closer to 20 euros). You can also ask the GRO to e-mail the copy back to you.
First Name: William
- Last Name: Mullen
- Year: 1881
- Year Of Death: 1881
- Registered Quarter/Year: Jul - Sep 1881
- Age: 61
- Year Of Birth: 1820
- Registration District: Rathdrum
- Volume: 2
- Page: 646