Cover-Up

[Red]

Hi Folks. This is out of my area of expertise so I'm hoping someone can offer a few suggestions. We recently had a crime scene involving an IED. I collected a red plastic 5 gallon gas container which had writing on it; however, the writing has been concealed with black marker. Is there any way to see through black marker on this type of surface?

[Steve Everist]

Do you have an Alternate Light Source? If so, you can experiment with different wavelengths of light with and without different filters.

Do you have a photo lab that does UV and IR photography?

[Red]

Yes, we have an alternate light source, which I will experiment with, but we do not have a photo lab that does UV and IR photography. I can certainly check the area to see if there is one that uses these methods.

[g.]

Yeah, Steve E. is absolutely right. The ink in the "marker" may react differently to varying wavelengths of light than the original ink writing below. (i.e. they will absorb the wavelengths of light differently, because of different chemical components...) so in effect one could make the magic marker writing disappear to make the writing under visible.

If your unit has a "Forensic Document Examiner (QD unit)" check with them. This is their bread and butter and part of their extensive training. They do this all the time with obliterated writing on checks and such.

Good luck

g.

[David Fairhurst]

If the light technique doesn't work you could look at removing the marker ink with a differentiating solvent. i.e. one that will remove the marker pen but not the original writing.
If the original writing is something printed on the container by the maufacturer or distributor this shouldn't be a problem as they will have used an ink that will not be dissilved by petroleum spirit (due to it being a gas can), so I would start with this. Xylene is a common solvent used in marker pens so this would be my next choice. I'd then go on to try acetone, ether, alcohol and acetic acid.
Obviously you'll have to be careful until you find the right solvent so as not to remove everything in one go.
Your real problem will be if the original writing was written with the same black marker pen as it was obliterated with. In this case neither optical nor chemical means will work.

[Jan Seaman Kelly]

Black marker is very difficult . Have you considered contacting an ink specialist with Secret Service........Gerry LaPorte may be able to provide guidance as to what method might work to raise the original writing....or the solvent to use to remove the marker on a surface such as the one you are dealing with. Good luck

[Steve Everist]

Our photo lab just did this with some black ball point pen that was covered with black felt tip. He was quite successful with just using the ALS.

It's trial and error, but I'd start with the ALS.

[David Fairhurst]

Absolutely Steve, nondestructive techniques should always be tried first.
One more cautionary note about solvents. Make sure they don't dissolve the can itself!

David

[Red]

Although I cannot confirm that the writing underneath the black marker is made with the same black marker... I'm afraid that it is. I've used the ALS, which has now provided me with one word which appears to be with the marker as well. Still have 5 more words to go. I have been in contact with a document examiner, who is having a hard time with the thick plastic surface of the container, however, I have not contacted a specialist with the Secret Service as this will be my next step before applying a solvent in an attempt to remove the marker.

[Larry Mazzola]

Have you tried infrared photography? I seem to remember this technique was used for examining documents

[Red]

I did use IR Larry, but to no avail.

[Ducky]

Use of transmitted lighting with long exposures( several minutes) may record the difference of density of the original writting and the cover up marking.

you would have to cut the gas can to photograph from the inside surface.