Reference letter co-signing

[pax6pax6]

I am applying to a few PhD programs in the biological sciences and as such, need to get a few reference letters. My problem is that in the few research positions I have had, I have never been that close with the PI in the lab. Would it be appropriate to ask the graduate student who supervised me to write the letter, and ask the PI to co-sign the letter? I could directly ask the PI, but I think that the situation I outlined would lead to a less generic assessment of my skill set. 

Is this a common thing to do? Any suggestions or advice would be appreciated.

[Eigen]

You would generally ask the PI of the lab to write the letter, and they get information from the graduate student you worked with as appropriate. 

I've had my PI ask me for this several times for undergraduates who worked with me. 

If you're really worried about it, approach the graduate student before you approach the PI, and they can talk to the PI about writing some portions of the letter.

Edited October 5, 2015 by Eigen

[fuzzylogician]

Yes, you could do that and in this case it sounds like it would be a good idea. It would get you the benefit of a detailed letter along with an established name at the bottom. The student most likely isn't the most experienced at writing these letters, so it would help them to have the PI involved and could be a learning opportunity for them too, if they want to view it that way.